Illegal Immigration: Border-Crossing Deaths Have Doubled Since 1995; Border Patrol's Efforts to Prevent Deaths Have Not Been Fully Evaluated.
Published: 2006-08-15T00:00:00

Fast Facts:

Highlights:
section_title: Why GAO Did This Study
paragraphs: Reports in recent years have indicated that increasing numbers of migrants attempting to enter the United States illegally die while crossing the southwest border. The Border Patrol implemented the Border Safety Initiative (BSI) in 1998 with the intention of reducing injuries and preventing deaths among migrants that attempt to cross the border illegally. GAO assessed: (1) Trends in the numbers, locations, causes, and characteristics of border-crossing deaths. (2) Differences among the Border Patrol sectors in implementing the BSI methodology. (3) The extent to which existing data allow for an evaluation of the effectiveness of the BSI and other efforts to prevent border-crossing deaths.
section_title: What GAO Found
paragraphs: GAO's analysis of data from the BSI, the National Center for Health Statistics (NCHS), and studies of state vital registries shows consistent trends in the numbers, locations, causes, and characteristics of migrant border-crossing deaths that occurred along the southwest border between 1985 and 2005. Since 1995, the number of border-crossing deaths increased and by 2005 had more than doubled. This increase in deaths occurred despite the fact that, according to published estimates, there was not a corresponding increase in the number of illegal entries. Further, GAO's analysis also shows that more than three-fourths of the doubling in deaths along the southwest border since 1995 can be attributed to increases in deaths occurring in the Arizona desert. Differences among the BSI sector coordinators in collecting and recording data on border-crossing deaths may have resulted in the BSI data understating the number of deaths in some regions. Despite these differences, our analysis of the BSI data shows trends that are consistent with trends identified in the NCHS and state vital registry data. However, the Border Patrol needs to continue to improve its methods for collecting data in order to accurately record deaths as changes occur in the locations where migrants attempt to cross the border--and consequently where migrants die. Improved data collection would allow the Border Patrol to continue to use the data for making accurate planning and resource allocation decisions. Comprehensive evaluations of the BSI and other efforts by the Border Patrol to prevent border-crossing deaths are challenged by data and measurement limitations. However, the Border Patrol has not addressed these limitations to sufficiently support its assertions about the effectiveness of some of its efforts to reduce border-crossing deaths. For instance, it has not used multivariate statistical methods to control for the influences of measurable variables that could affect deaths, such as changes in the number of migrants attempting to cross the border.

section_title: Letter
paragraphs: Reports by GAO and others in recent years have indicated that increasing  numbers of migrants attempting to illegally enter the United States die  while crossing the southwest border in remote, desert areas or in other  areas with particularly rugged and dangerous terrain. The U.S. Border  Patrol implemented the Border Safety Initiative (BSI) in June 1998 with  the intention of enforcing border security, educating and informing  migrants of the dangers involved in crossing the border illegally, and  carrying out search and rescue operations to help migrants in life- threatening situations. Additionally, the Border Patrol implemented the  Arizona Border Control Initiative (ABCI) and the Interior Repatriation  Program (IRP), efforts that also include components designed to reduce  migrant deaths. As part of the BSI’s mission, the Border Patrol established  a methodology that outlines procedures to identify, track, and record data  on migrant border-crossing deaths and rescues. The BSI methodology  defines border-crossing deaths as those occurring in furtherance of an  illegal entry and includes guidelines for recording those deaths occurring  within its target zone—an area consisting of 45 counties on or near the  southwest border with Mexico. These 45 counties are within an area that  includes 9 of the 20 Border Patrol sectors responsible for enforcing U.S.  borders and securing official ports of entry (see fig. 1). According to BSI  reports, since fiscal year 1998, there has been an upward trend in the  number of migrant border-crossing deaths annually, from 266 in 1998 to  472 in 2005, with some fluctuations over time.
In light of concerns about reported increases in border-crossing deaths  and interest in the BSI’s approach to tracking and reducing these  incidents, you asked us to analyze federal data on border-crossing deaths  as well as available data on the Border Patrol’s efforts to reduce such  deaths. Specifically, for this report, we assessed: (1) How do the Border  Patrol’s data on trends in the numbers, locations, causes, and  characteristics of border-crossing deaths compare to other sources of data  on these types of deaths? (2) What differences, if any, are there in how the  Border Patrol has implemented the BSI methodology across its sectors?  (3) To what extent do existing data allow for an evaluation of the  effectiveness of the BSI and other Border Patrol efforts to prevent border- crossing deaths?
You also asked us to compare deaths among migrants to deaths in the  general U.S. population living within the BSI target zone. We compared  each group’s share of deaths for the causes of death most commonly  associated with border-crossing (see app. IV).
To address our objectives, we analyzed data on migrant border-crossing  deaths that occurred between 1990 and 2005 within the BSI target zone— which includes 45 counties on or near the border in California, Arizona,  New Mexico, and Texas. We analyzed data on border-crossing deaths  recorded by the Border Patrol in the Border Safety Initiative Tracking  System (BSITS) for fiscal years 1998 through 2005. We also analyzed data  from the National Center for Health Statistics (NCHS) mortality files from  the National Vital Statistics System for the years 1990 through 2003, the  most recent year for which NCHS data were available at the time we did  our work. The NCHS data contain information from death certificates for  all deaths occurring within the United States, regardless of the cause of  death. Because death certificates do not explicitly identify deaths as  border-crossing deaths, we used information about place of birth,  residence, and cause of death to identify likely incidents of migrant deaths.  These estimates may either under or over count actual border-crossing  deaths, depending on a number of factors (see app. I for additional  discussion). We assessed the reliability of both sources of data and  determined that they were sufficiently reliable for our purposes of  describing trends in deaths over time and across locations. We then  supplemented our analysis of these data by reviewing data on transient  migrant deaths reported in studies by the University of Houston’s Center  for Immigration Research (CIR) that used state vital registry data to  estimate the number of border-crossing deaths among migrants for the  years 1985 through 1998. Because both the NCHS and state vital registry  data are collected independently of the Border Patrol’s efforts to collect  BSI data, we used them to corroborate or refute the trends that were  identified in our analysis of the BSI data. (For details regarding our  methods for analyzing the data, see app. I.) In addition to the data analysis,  we reviewed the written BSI methodology for tracking and recording  deaths in the BSITS database, and we interviewed Border Patrol officials  at Department of Homeland Security headquarters in Washington, D.C., as  well as officials in the nine southwest Border Patrol sectors, about issues  related to migrant border-crossing deaths and the BSI. We also reviewed  the methods for collecting data on border-crossing deaths used by county  coroners and medical examiners that track these deaths and reviewed the  studies on migrant border-crossing deaths conducted by CIR, as well as a  study by researchers at the Centers for Disease Control and Prevention  (CDC). Finally, we interviewed journalists, officials from various  advocacy groups, and state and local health officials in Arizona, New  Mexico, and California.
We conducted our work between August 2005 and June 2006 in  accordance with generally accepted government auditing standards.
subsections: section_title: Background
paragraphs: In 1994, the Attorney General announced plans for the Southwest Border  Strategy, an enforcement initiative designed to strengthen enforcement of  the nation’s immigration laws and to shut down the traditional corridors  for the flow of illegal immigration along the southwest border. The  strategy called for the former Immigration and Naturalization Service  (INS) to incrementally increase control of the border in four phases with  the goal of making it increasingly difficult and costly for migrants to  attempt illegal entry so that fewer individuals would try. The strategy  called for adding resources along the southwest border by first  concentrating personnel and technology in those sectors with the highest  levels of illegal immigration activity (as measured by apprehensions) and  by then moving to the areas with the least activity. Additional Border  Patrol resources were initially allocated in the San Diego, California, and  El Paso, Texas, sectors. The strategy assumed that as the urban areas were  controlled, the migrant traffic would shift to more remote areas where the  Border Patrol would be able to more easily detect and apprehend migrants  entering illegally. The strategy also assumed that natural barriers including  rivers, such as the Rio Grande in Texas, the mountains east of San Diego,  and the desert in Arizona would act as deterrents to illegal entry (see fig.  1).
As we reported in 2001, INS’ analysis of apprehensions data indicated that  the increased enforcement efforts in the San Diego and El Paso sectors  that began in 1994 ultimately resulted in the redirection of migrant flows to  eastern California and the Sonoran Desert of Arizona. However, INS did  not anticipate the sizable number of migrants that would continue to  attempt to enter the United States through this harsh terrain. Studies of  migrant deaths along the southwest border at the time concluded that,  while migrants had always faced danger crossing the border and many  died before INS began the Southwest Border Strategy, following the  implementation of the strategy, there was an increase in border-crossing  deaths resulting from exposure to either extreme heat or cold.
subsections: section_title: The Border Patrol Implemented the Border Safety Initiative in June 1998
paragraphs: In response to concerns about the number of migrants who are injured or  die while attempting to cross the border, the INS implemented the Border  Safety Initiative (BSI) and a number of related programs beginning in June  1998. These initiatives were implemented in conjunction with the Border  Patrol’s ongoing enforcement efforts; the Border Patrol views the BSI and  related efforts to prevent deaths as complementary to its primary mission  of enforcing the law and securing the border. The primary objectives of  the BSI are to reduce injuries among migrants and to prevent migrant  deaths in the southwest border region. Many migrants suffer severe  dehydration and heat exhaustion as a result of attempting to cross the  desert where temperatures can exceed 115 degrees in the summer. Agents  provide assistance to migrants who are stranded and may supply food,  water, and medical care to migrants who become injured or lost in the  course of attempting to cross the border.
As part of the BSI’s efforts to prevent migrant deaths, several of the Border  Patrol sectors in the BSI target zone have rescue beacons installed in those  areas of the desert considered to be especially dangerous for migrants  attempting to cross the border. Each beacon has a button that migrants  can push to activate a sensor, thus alerting nearby Border Patrol agents  that they are in need of help. Each sector also has a number of specialized  search and rescue units known as Border Patrol Search, Trauma, and  Rescue (BORSTAR) teams. BORSTAR agents have specialized training in a  number of areas including medical skills, technical rescue, navigation,  communication, swiftwater rescue, and air operations in order to prepare  them to carry out emergency search and rescue operations. BORSTAR  units conduct search and rescue operations as part of the Border Patrol’s  ongoing efforts to enforce and secure the border. As of October 2005, the  Border Patrol had deployed 164 BORSTAR agents within its nine Border  Patrol sectors along the southwest border.
The Interior Repatriation Program (IRP) and Lateral Repatriation Program  (LRP) are additional initiatives designed by the Border Patrol to prevent  deaths and to discourage migrants from crossing the border in dangerous  areas of the desert. The IRP was implemented in 2004 in conjunction with  the Mexican government with the goal of removing migrants from those  areas considered to be smuggling corridors in an effort to break the cycle  of illegal immigration among those migrants who make repeated attempts  to cross the border following apprehension. The program transports  migrants who are apprehended in the Tucson and Yuma Sectors, and who  volunteer for the program, to their hometowns in the interior of Mexico,  rather than deporting them to points along the Arizona border where they  may be more likely to attempt to cross again. Similarly, the LRP was  implemented when the United States was unable to negotiate an  agreement to return migrants to the interior of Mexico with the Mexican  government in September 2003. Migrants apprehended in Arizona were  instead transported to ports of entry in Texas in an effort to discourage  them from attempting multiple crossings in the desert.
In response to the escalating problems with illegal immigration in Arizona,  the Border Patrol also implemented the Arizona Border Control Initiative  (ABCI) in 2004 as a multi-disciplinary initiative with the goal of  coordinating federal, state, and local authorities to control the Arizona  border. The ABCI strategy focused on confronting illegal immigration  along the western part of the Arizona desert before it reached the United  States. Components of the program included a media campaign warning  migrants of the dangers associated with crossing the border and increased  infrastructure and manpower along the Arizona border. While not  intended primarily as a safety initiative, the enhanced infrastructure and  increased manpower associated with the ABCI also allowed Border Patrol  officers to better track and rescue migrants and to prevent deaths.  Additional components of the program include roving patrols, camp  details, and air support, and included increased assistance with highway  patrols from state, local, and tribal authorities.
The Border Patrol has also implemented a number of additional efforts to  discourage migrants from attempting to cross the border as part of the  BSI’s prevention component. Prevention efforts have included  broadcasting public service announcements in Mexico about the risks  involved in hiring smugglers and posting signs in high-risk areas to warn  potential crossers of the dangers at the border. Because many migrants  attempting to enter the United States illegally may not carry identification,  the BSI also attempts to identify those who have died while crossing the  border. Border Patrol officers work in conjunction with Mexican  Consulates in the region in order to identify migrants who may have been  reported missing by friends or family.
In 2000, the BSI also began formally tracking and recording data on  migrant rescues and deaths through the establishment of a database  known as the Border Safety Initiative Tracking System (BSITS). BSI data  are used by the Border Patrol for tracking numbers and locations of  deaths and rescues, identifying trends and high-risk areas, allocating  resources for BSI projects, and measuring the effectiveness of various  programs and projects that are related to the BSI. The database includes  information such as cause and location of death as well as the decedent’s  gender and nationality. In order to ensure consistent tracking and  recording of incidents along the southwest border, the BSI has developed  a formal, written methodology that outlines the roles and responsibilities  of each BSI sector coordinator in collecting and recording data on migrant  deaths and rescues. The methodology also outlines definitions for the  types of incidents that should be recorded in the BSITS database. The  methodology defines a BSI-related death as a death involving an  undocumented migrant in furtherance of illegal entry within the BSI target  zone, or deaths occurring outside the target zone when the Border Patrol  was directly involved. The methodology includes detailed instructions  regarding the time frame for reporting incidents, protocols for entering  and updating information recorded in BSITS, and guidelines for coding  incidents using appropriate rescue and cause of death categories. In order  to ensure that all migrant border-crossing deaths in the target zone are  reported, the methodology also specifies that BSI sector coordinators  should establish contact with local medical examiners or county coroners  as well as Mexican Consulates in the region about those deaths where the  Border Patrol was not involved in order to record the deaths in the BSITS  database.
section_title: Various Groups Track and Record Border-Crossing Deaths Using Different Methodologies That Can Lead to Differing Counts of Deaths
paragraphs: A number of groups in addition to the Border Patrol have also attempted  to track incidents of border-crossing deaths. Advocacy groups, media  outlets, medical examiners’ offices in some border counties, researchers at  the CDC, and the Mexican government are among the organizations that  have collected and reported data on border-crossing deaths, but each uses  a different methodology to count and record deaths. All agree that a  border-crossing death involves a migrant who dies in the course of  attempting to cross illegally into the United States. However, each may  operationalize the definition differently and rely on a variety of sources of  information for making determinations about which deaths to include in  their counts. For example, the “Victoria 19”—an incident in which 19  migrants who were smuggled in the back of a tractor-trailer were all found  to have suffocated near Victoria, Texas, in 2002—would not be included in  the Border Patrol’s counts of migrant border-crossing deaths because it  occurred outside the BSI target zone and there was no direct Border  Patrol involvement in the case. By contrast, some advocacy groups that  track and record border-crossing deaths include the Victoria 19 in their  totals. Because the incident involved migrants who were in transit across  the border into the United States, they consider it a border-crossing death,  even though it occurred outside the Border Patrol’s identified BSI target  zone.
In making decisions about whether or not to count the death of an  unidentified person as a border-crossing death, Border Patrol officials and  others may rely on professional judgment of circumstantial evidence. This  may also result in differing counts of deaths from one group to the next.  For example, data on border-crossing deaths maintained by the Pima  County Medical Examiner’s office for the Tucson area have been cited by  the media in news reports. Some cases of border-crossing deaths may  involve unidentified bodies that were discovered in the desert; these cases  can often include skeletal remains or decomposed bodies. In determining  whether to count these incidents as border-crossing deaths, the Pima  County Medical Examiner’s office uses information about where a body is  found—for example, along a known migrant corridor—as well as other  circumstantial evidence such as the decedent’s clothing or personal effects  that may indicate a country of origin. The Pima County Medical  Examiner’s office reported that it records all cases of migrant deaths  including a few cases involving migrants who die of natural causes such as  heart attacks or appendicitis, noting that, if there is evidence that the  person died while in transit between Mexico and the United States, the  office will count it as a border-crossing death regardless of the cause.  However, the Pima County Medical Examiner’s office places some  limitations on which cases it records as border-crossing deaths. For  example, the office attempts to exclude any cases involving illegal  immigrants who had established residency in the United States from its  counts of border-crossing deaths in order to distinguish deaths occurring  among illegal immigrants who had been living and working in the United  States for some time from migrants who died in the course of attempting  to cross the border.
Using another method to measure migrant border-crossing deaths,  researchers at the CDC designed a study to track and record migrant  border-crossing deaths occurring in U.S. border counties in Arizona, New  Mexico, and Texas between 2002 and 2003. They requested that medical  examiners in these states provide them with information about cases that  met a number of standardized criteria. The researchers then reviewed the  death certificates and other information about these cases in order to  describe trends in border-crossing deaths. They asked medical examiners  to include only those cases involving decedents who were found in one of  several selected U.S. counties along the U.S. border with Mexico, whose  immigration status was determined to be unauthorized, and who were  determined to have died during transit from Mexico into the United States  within 30 days of their arrival in the country. According to their  methodology, an unauthorized decedent was identified based upon one or  more of the following criteria: a person who was identified as not being a  legal resident or an authorized entrant into the United States, a person  who was identified as a resident of another country based upon reports by  family, friends, or officials, or a person who was identified as being a  resident of another country based upon analysis of circumstantial  evidence found with the decedent. Such circumstantial evidence included  tattoos, items found on or near the body, personal items found in bags,  clothes, and documents including birth and marriage certificates.  Decedents were not included in the study if they were known to have  resided illegally in the United States for more than a month before their  death, if they were determined not to have died while crossing the border,  or if they had died after being treated in a U.S. border hospital.
Table 1 illustrates the counts recorded by some of the groups attempting  to track and record border-crossing deaths in Pima County, Arizona,  between 2002 and 2005.
section_title: BSI and NCHS Data Show That, Since the Late 1990s, Increases in Deaths along the Southwest Border Were Accounted for by Increases in Deaths in the Tucson Sector
paragraphs: Our analysis of the BSI and NCHS data shows consistent trends in the  numbers, locations, causes, and characteristics of deaths over time.  Consistent with reported trends in prior studies of border-crossing deaths,  our analysis of both data sources shows an increase in the overall  numbers of deaths occurring along the southwest border between 1998  and 2005 following a decline between 1990 and 1994. Our analysis of the  NCHS data shows that the number of deaths doubled from the mid-1990s  through 2003, and our analysis of the BSI data shows that the majority of  the increase in deaths that occurred between 1998 and 2005 was  concentrated within the Border Patrol’s Tucson Sector. Consistent with  the increase in Tucson, the number of border-crossing deaths due to heat  exposure also steadily increased beginning in 1998. While the majority of  deaths have occurred among men, according to our analysis of the BSI  data, deaths among women increased from 9 percent of all deaths in 1998  to 21 percent of all deaths in 2005. Further, increases in deaths among  women in the Tucson Sector accounted for the majority of the overall  increase in deaths among women in all sectors. The increase in the  number of deaths in the Tucson Sector between 1998 and 2005 occurred  despite the fact that the number of apprehensions of illegal immigrants  recorded by the Border Patrol in the Tucson Sector had declined following  a peak in 2000. To the extent that apprehensions are correlated with the  number of attempted crossings, the increase in deaths in the Tucson  Sector indicates that the desert is a particularly difficult region for  migrants attempting illegal entry.
subsections: section_title: BSI and NCHS Data Show Consistent Trends in Numbers, Locations, and Causes of Death
paragraphs: Our analysis of the BSI data as well as our analysis of the NCHS data  reveals trends that are consistent with trends identified in previous studies  by CIR examining the numbers, locations, and causes of border-crossing  deaths over time. All three sources of data show that trends in migrant  deaths follow a somewhat U-shaped curve as deaths within the BSI target  zone increased beginning in the mid-1990s following a period of decline  between 1990 and 1994 (see fig. 2). We used NCHS data—which are based  on death certificates filed by local coroners and medical examiners  throughout the country and include records of all deaths that occur within  the United States, regardless of the decedent’s country of origin—as an  independent data source to corroborate trends identified in the BSI data.  Additionally, the trends in the NCHS data between 1990 and 1998 are also  consistent with the trends in border-crossing deaths reported by Karl  Eschbach and his colleagues at the Center for Immigration Research in  their analysis of state-level vital registry data. Differences in the total  numbers of deaths in the NCHS and CIR data arise from the differences in  the methodologies used by each. Our analysis of the NCHS data shows  that deaths declined in the San Diego and El Centro Sectors between 1990  and 1994 and that over this period, deaths from traffic fatalities and  homicide also declined. This pattern represents a major shift in the causes  of migrant border-crossing deaths, as traffic fatalities were the leading  cause of migrant border-crossing deaths during the early 1990s, while from  the late 1990s onward, heat exposure was the leading cause of death.  Additionally, according to our analysis of the NCHS data, homicides  decreased from 24 percent of all deaths in 1990 to 9 percent in 2003. Our  analysis of the BSI data also shows that heat exposure was the leading  cause of death from 1998 to 2005. The increase in deaths due to heat  exposure over the last 15 years is consistent with our previous report that  found evidence that migrant traffic shifted from urban areas like San  Diego and El Paso into the desert following the implementation of the  Southwest Border Strategy in 1994.
Our analysis of the BSI data shows that the total number of border- crossing deaths increased from 254 in 1998 to 334 in 2003 and then  increased to 472 in 2005. Similarly, our analysis of the NCHS data shows  that the number of deaths increased from 219 in 1998 to 365 in 2003.  Corresponding with the increases in deaths that occurred between 1998  and 2005, border-crossing deaths also became increasingly concentrated  within the Tucson Sector—a region that corresponds with Arizona’s  portion of the Sonoran Desert. For example, our analysis of the BSI data  shows that the Tucson Sector’s share of all border-crossing deaths  increased tenfold, from 4.3 percent of all deaths in 1998 to 45.8 percent in  2005 (see fig. 3), so that by 2005, of the 472 deaths that occurred across all  nine southwest sectors, 216 occurred within the Tucson Sector. Our  analysis of the NCHS data shows a similar trend, in that the Tucson  Sector's share of border-crossing deaths increased at least threefold  between 1998 and 2003. The total number of deaths in the eight other  Border Patrol sectors remained relatively constant over this period.
Further, the increase in deaths occurring within the Tucson Sector  accounted for the majority of the increase in deaths along the southwest  border. For example, our analysis of the NCHS data indicates that the  increase in deaths in the Tucson Sector from 1990 to 2003 accounted for  more than 78 percent of the total increase in border-crossing deaths along  the entire southwest border. Across all sectors during these years, the  total number of border-crossing deaths increased by 195, and of that  increase, 153 deaths occurred in the Tucson Sector. Our analysis of the  BSI data shows a similar result: between 1998 and 2005, deaths across all  sectors increased by 218, and the Tucson Sector accounted for 205—or   94 percent—of the increase. The increase in deaths in the Tucson Sector is  also consistent with the shifting of migrant traffic from urban areas in San  Diego and El Paso into the desert following the implementation of the  Southwest Border Strategy. The increase in deaths in the Tucson Sector  occurred after the number of deaths occurring within the San Diego Sector  declined, beginning in the early 1990s (see fig. 8 in app. II). In 1990, the San  Diego Sector accounted for over one-third of all border-crossing deaths.  By 2003, the San Diego Sector accounted for only 8 percent of all deaths.
While much of the migrant traffic appears to have shifted to sectors east of  San Diego like Tucson, a similar shift does not appear to have occurred in  the sectors east of El Paso. Border Patrol officials have noted that there  are few population centers on the Mexican side of the border in those  regions that might serve as a starting point for migrants intending to cross.  Similarly, on the U.S. side of the border, sectors like Marfa in western  Texas are more sparsely populated. Border Patrol officials have  speculated that fewer migrants attempt to cross in these areas because  they largely consist of small towns and communities. Consequently,  migrants may have to walk longer distances to reach a population center  and may face an increased risk of being apprehended as a result of being  noticed by the local population or Border Patrol agents.
As the number of deaths occurring within the desert in and around the  Tucson Sector increased, so too did the number of deaths due to heat  exposure. While there has been an overall increase in the number of heat  exposure deaths between 1994 and 2005, there have been some  fluctuations between years. These fluctuations may be due to factors such  as temperature changes from one year to the next as higher desert  temperatures in some summers may result in an increase in migrant  deaths. Our analysis of both the BSI and NCHS data shows increases in the  total percentage of border-crossing deaths due to heat exposure over time.  For example, by 2001, heat exposure deaths in the BSI data accounted for  more than one-third of all deaths. Our analysis of the NCHS data also  shows that by 2001 heat exposure deaths accounted for more than   30 percent of all border-crossing deaths, an increase from about 4 percent  in 1990 (see fig. 4).
As the number of deaths due to heat exposure increased, the number of  deaths due to traffic-related fatalities, homicide, and drowning either  remained relatively constant or declined (see fig. 5). For example, our  analysis of the NCHS data shows that traffic fatalities declined from more  than half of all border-crossing deaths in the early 1990s to less than   30 percent of deaths by 2003. Our analysis of the BSI data shows similar  trends, with deaths due to exposure increasing from 107 to 185 while  deaths due to motor vehicle accidents, homicide, and drowning  decreased slightly from 109 to 103 between 1998 and 2005. Our analysis  of the NCHS data also shows that homicides have also declined slightly,  accounting for 41 border-crossing deaths in 1990, and 33 deaths in 2003.  Despite the decline in homicides, Border Patrol officials have noted an  increase in border-related violence among smugglers and migrants  including assault and robbery, though officials stated that few incidents  have resulted in deaths thus far.
section_title: Risk Associated with Border Crossing Appears to Have Increased in Recent Years
paragraphs: The risk associated with attempting to cross the border illegally also  appears to have increased between 1998 and 2004. While the number of  migrant border-crossing deaths approximately doubled over this period,  estimates of undocumented migration into the United States—whether  based on U.S. census data or based on the number of Border Patrol  apprehensions of migrants attempting illegal entries—do not show a  corresponding increase. For example, estimates of illegal entries into the  United States indicate that from 1998 through 2004, the estimated number  of such entries has declined by 16 percent. Similarly, the number of  apprehensions of persons attempting illegal entry has declined by   25 percent over this same period. At the same time, our analysis of the BSI  data shows that the number of border-crossing deaths increased by about  29 percent from 254 in 1998 to 328 in 2004. (See app. I for a discussion of  our methodology.) An examination of the increase in the number of deaths  in relation to declines in the estimated number of illegal entries suggests  that the risk associated with crossing the border has increased in recent  years.
This apparent increase in risk associated with attempting to cross the  border illegally also appears to be concentrated in the Tucson Sector. The  increase in the number of border-crossing deaths from 1998 through 2005  was generally independent of changes in the number of apprehensions of  migrants attempting illegal entries within the sector, especially during the  decline in apprehensions that occurred between 2000 and 2002 (see fig. 6).  In other sectors, the number of apprehensions generally correlated with  the number of deaths: as apprehensions increased, deaths show a  corresponding increase, and conversely, as apprehensions declined,  deaths generally also declined, although the amount of change in deaths  and apprehensions between years differed (see fig. 7).
While there are limitations to using the number of apprehensions as a  measure of attempted illegal entries into the United States, we previously  reported that changes in apprehensions can provide some evidence of  shifting illegal migration patterns. However, to the extent that  apprehensions can be used as an indication of attempted illegal entries  into the United States, unlike other estimates of illegal entries, these data  have the advantage of being sector-specific and, therefore, allow for  comparisons between sectors in estimating attempted illegal entries and  deaths. In the Tucson Sector, apprehensions increased from 1998 to 2000  and then generally declined from 2000 to 2005, with some year-to-year  fluctuations. While apprehensions generally declined, the number of  border-crossing deaths in the Tucson sector continued to increase over  the same period. To the extent that an increased number of apprehensions  generally can be assumed to represent an increased number of migrants  attempting illegal entry, the inverse relationship between apprehensions  and deaths in Tucson suggests that deaths have increased despite the fact  that there has not been a corresponding increase in the number of people  attempting to cross in that sector.
The reasons for this phenomenon are unclear. There are a number of  factors that may make the desert in and around Tucson a particularly  dangerous region for migrants to navigate, including the difficulty of the  terrain, extreme summer temperatures, and the increased use of  smugglers in the sector. While there is evidence that increasing numbers of  migrants have employed smugglers to help them cross the border illegally  across all nine southwest Border Patrol sectors in recent years, smuggling  may be especially dangerous in the Tucson Sector. Border Patrol officials  reported that migrants who are unable to keep up with smugglers may be  left behind in extreme desert temperatures without sufficient food or  water. Alternatively, the inverse relationship between apprehensions and  deaths in the Tucson Sector could arise if apprehending migrants has  become more difficult in Tucson than in other sectors. This could result  from a number of factors such as changes in the number of agents  assigned to patrol the sector or the number of migrants who are able to  evade apprehension by attempting to cross in particularly remote areas of  the sector.
section_title: While the Majority of Border-Crossing Deaths Occur among Men, the Increase in Deaths among Women Occurred Largely in the Tucson Sector
paragraphs: According to our analysis of the NCHS data, males comprised more than  78 percent of the border-crossing deaths occurring between 1990 and 2003,  and persons between 15 and 44 years of age comprised 79 percent of all  deaths. The trends over time in these respective shares of deaths were  relatively constant with some minor, year-to-year fluctuations. Our  analysis of the BSI data shows similar trends between 1998 and 2005, with  males accounting for 83 percent of all deaths, and persons between the  ages of 15 and 44 comprising 88 percent of all deaths. This was true across  all sectors with trends remaining relatively constant across years. While  deaths among women were consistently much lower than men, there was  an increase in the overall number of female deaths that occurred between  1998 and 2005—the number of female deaths increased from 22 to 90, or  from 9 percent to 21 percent of all deaths. Our analysis of the BSI data  shows that, between 1998 and 2005, the increase in deaths among females  in the Tucson Sector accounted for 57 percent of the total increase in  deaths among women across all sectors. Similarly, our analysis of the  NCHS data shows that from 1990 to 2003, the increase in deaths among  females in the Tucson Sector accounted for 96 percent of the total  increase in deaths among women across all sectors.
section_title: The Border Patrol’s Approach to Tracking and Recording Deaths Has Not Been Implemented Consistently across Sectors
paragraphs: The BSI’s methodology for collecting data on border-crossing deaths  provides a framework for gathering and recording data on the number of  migrant deaths that occur in each sector. While the Border Patrol has  taken steps to improve the collection of its data over time, differences  remain among the nine BSI sector coordinators in how each has  implemented the methodology, and these differences could result in  incomplete counts of border-crossing deaths in any given year.  Additionally, because of inherent uncertainties associated with  determining whether some migrant deaths are border-crossing deaths, an  exact count of all deaths may not be possible to obtain.
subsections: section_title: Differences in the Implementation of the BSI Methodology across Sectors May Result in Incomplete Counts of Border-Crossing Deaths
paragraphs: The BSI methodology specifies that each sector coordinator should track  all migrant deaths occurring within the sector, including those deaths that  may have first come to the attention of local authorities by obtaining and  sharing information with county coroners or medical examiners. However,  BSI sector coordinators have the latitude to decide how to implement this  outreach. Some coordinators reported regularly scheduled contact with  local authorities, while others stated that communication was informal  and infrequent. Some coordinators also reported that the nature and  methods for communicating with local authorities had changed from one  year to the next. For example, local medical officials in one county where  a relatively large number of deaths occurred reported that Border Patrol  officials in the Tucson Sector only began contacting them in 2005 to  request information on border-crossing deaths. As a result, the BSI data  prior to that year may not have included records of those border-crossing  deaths that were discovered by local authorities but that did not come to  the attention of Border Patrol officials. To the extent that they may not  include data on all border-crossing deaths recorded by local officials, the  BSI data may represent an undercount of the total number of border- crossing deaths in that sector. These undercounts may affect the Border  Patrol’s ability to understand the scale of the problem in each sector and  also impact its ability to continue to make accurate resource allocations  along the southwest border.
Since January 2005, the National BSI Coordinator has taken steps to  further clarify the methods that sector coordinators should use to  collaborate with local officials in collecting BSI data. However, the revised  BSI methodology does not specify the frequency with which sector  coordinators are to conduct this outreach nor does it outline the methods  that coordinators should use to share information about migrant deaths  with county coroners or local medical examiners. While all coordinators  reported some degree of contact with local authorities, communication  remains informal in some sectors. As a result, Border Patrol officials in  these sectors may not learn about all cases of migrant deaths, particularly  in smaller counties where border-crossing deaths occur with less  frequency. Border Patrol officials in those sectors reporting informal or  infrequent communication stated that they did not believe that these  omissions would likely have a significant impact on the total number of  deaths recorded in the BSITS database. While our analysis of the NCHS  data confirms these sectors have had relatively few deaths in recent years,  those trends have the potential to change in the future. For example, our  analysis of the BSI data shows only 11 deaths in the Tucson Sector in 1998.  However, as migration shifted from the San Diego Sector to the Tucson  Sector following the implementation of the Southwest Border Strategy, the  number of deaths in Tucson increased significantly. By 2005, Tucson  accounted for nearly half of all deaths recorded across all nine sectors,  with a total of 216 deaths. Since the current BSI methodology gives each  sector coordinator the latitude to determine how to approach  communication with local authorities about border-crossing deaths,  differences between sectors in implementing the BSI methodology may  ultimately affect the Border Patrol’s counts of border-crossing deaths in  the future. In addition, the nature and frequency of each sector’s contact  with local officials could potentially change each time a new sector  coordinator is assigned.
section_title: Identifying Border- Crossing Deaths May Be Difficult in Some Cases
paragraphs: Another factor that may affect the extent to which the Border Patrol  records the precise number of border-crossing deaths is the uncertainty  that arises in those cases involving bodies discovered in the desert or  other remote areas. In some of these instances both Border Patrol agents  and local medical examiners must use their professional judgment in  determining whether circumstantial evidence is sufficient to classify a  decedent as a migrant who died while in furtherance of an illegal entry.  Both Border Patrol officials and local medical examiners with whom we  spoke reported relying on such evidence as the type of clothing worn by  the decedent, whether or not the person was carrying water jugs (as  evidence that the person intended to travel some distance on foot), as well  as any personal documents or identification that might indicate country of  origin. Border Patrol officials and others also reported that, in many cases  where the decedent had no identification or only skeletal remains were  found, they may conclude that the decedent was a migrant attempting  illegal entry because the remains were found in a remote area that was a  known migrant-crossing corridor.
Further, determining when a migrant has arrived at his or her destination  and is no longer in furtherance of an illegal entry can involve making  judgments about the length of time a decedent was in the United States at  the time of death. In most cases of border-crossing deaths, when  decedents are found on known border-crossing trails or the deaths were  reported by other migrants attempting illegal entry, such determinations  can be made with some degree of certainty. However, in other  circumstances, the determination about how long a migrant had been in  the United States may be more difficult. For example, Border Patrol  officials reported cases of migrants who worked on a farm for a period of  a few weeks or even a month after arriving in the United States—to earn  funds to complete their migration—only to die while en route to their final  destination. Also, in cases involving skeletal remains, the determination  regarding whether to record the case as a border-crossing death may be  more difficult. Border Patrol officials and others generally reported that  they rarely encountered ambiguous cases where there was little or no  circumstantial evidence that provided some indication that the decedent  was a migrant who died while trying to cross the border. However, all  reported that, in the absence of being able to confirm the decedent’s  identity, they must use their best judgment to make an informed decision  about whether the death should be considered a border-crossing death.  Finally, the fact that a number of bodies may remain undiscovered in the  desert also raises doubts about the accuracy of counts of migrant deaths.  While local medical officials who track border-crossing deaths reported  that they do not believe that there are a large number of undiscovered  bodies that would add significantly to counts of border-crossing deaths,  the total number of bodies that have not been found is ultimately  unknown.
section_title: Evaluating the Effectiveness of the BSI and Other Border Patrol Efforts to Reduce Border- Crossing Deaths Presents Measurement Challenges
paragraphs: A number of measurement challenges and data limitations inhibit a  comprehensive evaluation of federal efforts to prevent border-crossing  deaths. In particular, because multiple factors may affect the numbers and  locations of migrant deaths, the effectiveness of the Border Patrol’s efforts  to prevent such deaths cannot be measured only by changes in the number  of deaths over time. Factors such as the number of people attempting to  cross the border in any given year, weather conditions, and the use of  smugglers may all affect the number and location of migrant deaths from  one year to the next. Similarly, clear cause and effect relationships  between migrant crossings, the Border Patrol’s enforcement efforts, and  prevention initiatives such as the BSI are difficult to determine. A decline  in deaths might incorrectly be associated with BSI activity. Some migrants  may be deterred by the Border Patrol’s enforcement efforts and not  attempt to cross at all, while others may attempt to cross in more  dangerous areas in an effort to avoid apprehension. In addition, because  Border Patrol agents typically carry out search and rescue activities  related to the BSI at the same time they carry out enforcement and  apprehension functions, it is difficult to isolate the impact that prevention  efforts may have had on the number of deaths.
subsections: section_title: A Number of Factors Would Need to Be Considered in Order to Assess Cause and Effect Relationships between Migrant Crossings, Border Enforcement, the BSI, and Related Efforts
paragraphs: Because multiple factors beyond the efforts of the BSI may potentially  affect the number of border-crossing deaths in any given year, the  influence of each would need to be taken into account and measured in  relation to the number of migrant deaths in order to accurately assess the  impact of the BSI. Measuring the effectiveness of the BSI in reducing  border-crossing deaths would require a comparison of changes in the  number of migrant deaths with changes in other causal factors—such as  the Border Patrol’s enforcement efforts, the number of migrants  attempting to cross the border illegally, and weather conditions, as well as  changes in how and where the BSI is implemented over time. Without  correcting for these factors, cause and effect relationships are difficult to  determine. For example, changes in the Border Patrol’s enforcement  efforts might lead to shifts in the locations where migrants attempt to  cross. If migrants attempt to cross in more dangerous areas of the desert  in order to avoid detection, this may lead to an increase in the number of  deaths. In this scenario, the BSI may in fact have prevented deaths through  its search and rescue operations, even though the number of deaths rose  as a result of more migrants crossing in the harsh desert terrain.  Alternatively, increased enforcement efforts may result in migrants being  apprehended before they are in danger or in need of rescue. Similarly, a  number of factors may also affect the number of migrants that attempt to  cross the border. For example, the dynamics of how many people attempt  to cross the border each year may be driven by the relative strength of the  U.S. labor market in relation to the Mexican labor market. In addition, the  number of migrants that make repeated attempts to cross the border until  they are successful may also change over time. Previous research suggests  that increased enforcement and harsh conditions have made crossing the  border more difficult; consequently, many migrants now pay smugglers to  help them cross. The increased difficulty and expense in crossing may  also result in fewer migrants making repeated attempts to cross the  border. Additionally, those who succeed in crossing may choose to stay  permanently in the United States rather than crossing back and forth for  seasonal employment as was the case in years past.
section_title: The Border Patrol Does Not Maintain Detailed Data on BSI Operations
paragraphs: If detailed data were available on the extent of the BSI’s efforts by sector,  it would be possible to more clearly isolate the program’s effects on trends  in deaths, while controlling for other factors that may affect deaths such  as increased enforcement efforts or weather fluctuations. However, the  Border Patrol does not maintain detailed data on where the BSI was used  over time that would be needed to conduct such an evaluation.  Specifically, the Border Patrol does not maintain historical data on the  number of hours agents dedicated exclusively to BSI activities or  historical data on apprehensions made by those agents who were  operating in their search and rescue capacity at the time of apprehension.  These data would provide necessary information about where the BSI was  used over time and allow for more precise measurements of the BSI’s  implementation across sectors. Because the Border Patrol’s primary  function is enforcement, agents typically carry out search and rescue  operations simultaneously with ongoing enforcement activities. As a  result, the extent to which the Border Patrol can isolate and record the  number of line hours and resources dedicated exclusively to BSI-related  activities is limited.
section_title: The Impact of Additional Border Patrol Programs in Reducing Migrant Deaths Has Not Been Demonstrated
paragraphs: Border Patrol has claimed that the Interior Repatriation Program (IRP)  resulted in a decrease in migrant deaths and that the decrease in deaths  was due, in part, to a lower recidivism rate among program participants  when compared with those migrants who did not participate in the  program. Border Patrol’s claims that the IRP contributed to reductions in  deaths were based upon a decline in the number of exposure deaths  recorded in the BSI data between 2003 and 2004. However, this simple  correlation does not constitute sufficient evidence of a causal effect of the  IRP on deaths. First, because participation in the program is voluntary, it  is not possible to determine the program’s impact on recidivism rates and  deaths with certainty. Those migrants who choose to be repatriated to  their hometowns in the interior of Mexico may be less motivated to  attempt reentry than those who elect not to participate in the program,  instead choosing to be returned to an entry point along the border. These  migrants may opt out of the program specifically because they intend to  try to cross the border again in the hopes of avoiding detection on their  next attempt. Further, in the second year of the IRP, the number of deaths  increased. If changes in the number of deaths were again used as the only  indication of the program’s effectiveness, the implication could be that the  IRP caused a corresponding increase in deaths between 2004 and 2005.  However, as we previously discussed, multiple factors in addition to the  Border Patrol’s efforts may affect the number of deaths in any given year.  For example, increased temperatures in the summer of 2005 may have  contributed to an increase in deaths when compared with the number of  deaths recorded for the same time frame in 2004.
A recent House of Representatives Appropriations Committee report  suggests that the Arizona Border Control Initiative (ABCI) was responsible  for 27 fewer deaths in the Tucson Sector between March 16, 2004, and  September 30, 2004—a 26-percent reduction in such deaths when  compared with the same location and time frame in 2003 prior to the  ABCI’s implementation. However, as we previously discussed, a number  of other factors such as changes in desert temperatures may also affect the  number of deaths from one year to the next. Like the Border Patrol’s  conclusions about the IRP, measuring changes in the number of deaths  between 2004 and 2005, without considering other factors, could imply  that the program resulted in an increase in deaths in 2005. Border Patrol  officials acknowledged that attributing reductions in exposure deaths to  the ABCI and IRP in 2004 was an overly simplistic correlation and that  many factors in addition to enforcement operations may contribute to the  number of deaths in any given year. Officials pointed to the fact that, in  2005, BORSTAR patrols began targeting illegal immigration corridors that  were experiencing high death rates. They reported that one result of  BORSTAR’s operations was that rescues of migrants in distress  significantly increased. However, officials also reported that, because  BORSTAR agents were operating in high-risk areas, they may have  discovered more bodies in the course of their patrols, also contributing to  an increase in Border Patrol’s total counts of deaths. Additionally, Border  Patrol officials recognized that their data collection methodologies may  also affect conclusions about the cause and effect relationships between  their efforts and migrant deaths. Officials stated that, because they  improved their methodology for collecting data on deaths starting in 2005,  deaths recorded by local coroners that were not routinely included in their  2004 counts may have also contributed to an increase in the number of  deaths they reported for the Tucson Sector in 2005.
section_title: Conclusions
paragraphs: Although the BSI data have some limitations and may undercount the  exact number of border-crossing deaths, the overall trends shown in the  data are corroborated by trends in both the NCHS data as well as the state- level vital registry data reported by CIR. The consistency in trends  identified in all three sources of data, as well as our assessment of the BSI  methodology, indicates that the BSI data can be used to provide valuable  information on trends in the numbers, locations, causes, and  characteristics of migrant border-crossing deaths over time. These trends  are particularly important for better understanding the scale of the  problem of migrant deaths and can provide useful information for making  key resource allocation decisions.
Although our analysis of the BSI data shows trends in border-crossing  deaths that are consistent with trends derived from other, independent  sources of data, we also note that not all BSI sector coordinators  consistently implemented the BSI methodology, and these differences can  contribute to incomplete counts of deaths. Some sectors have only  informal and infrequent communication with local authorities, while  others have regularly scheduled contacts with local medical examiners or  coroners about migrant deaths that may have occurred in the sector.  Because both the NCHS and BSI data indicate that the problem of migrant  border-crossing deaths has been growing in recent years, it is important to  continue to improve the available data about these deaths by refining  methods for tracking and recording deaths, including procedures for  communicating with local authorities in order to share information about  all potential cases of border-crossing deaths that occur within the BSI  target zone. The inconsistencies in the implementation of the BSI  methodology highlight opportunities to improve the quality of the Border  Patrol’s data on border-crossing deaths. Although there have been  relatively few deaths in the two sectors in which BSI coordinators use  informal methods to contact local authorities, these trends have the  potential to change. If patterns of undocumented migration were to shift,  as occurred in the Tucson Sector between 1998 and 2005, these informal  methods for contacting local officials could result in larger numbers of  unreported deaths. Similarly, since BSI sector coordinators currently have  the latitude to determine how they approach communication with local  officials, personnel changes could also result in changes in how each  sector implements the BSI methodology from one year to the next and  consequently affect counts of deaths.
Finally, the Border Patrol and others should be cautious about believing  assertions about the effectiveness of its prevention efforts, given the  difficulties involved in measuring the effects of such efforts. Claims about  cause and effect relationships are limited by the fact that multiple factors  affect the number of migrant border-crossing deaths from one year to the  next. While we recognize that the Border Patrol’s ability to measure BSI  activities separately from ongoing enforcement functions may be limited,  unless explicit controls are introduced to take into account the effects of  these factors, the effectiveness of prevention efforts cannot be  demonstrated.
section_title: Recommendations for Executive Action
paragraphs: In order to improve the consistency across Border Patrol sectors in the  implementation of the BSI methodology and the completeness of data on  deaths in any given year, we recommend that the Commissioner of  Customs and Border Protection take steps to ensure that BSI sector  coordinators follow a consistent protocol for collecting and recording  information about border-crossing deaths and that all coordinators follow  established procedures for maintaining and documenting regular contacts  with local authorities to obtain timely information about all border- crossing deaths within the BSI target zone.
In order to better demonstrate the effectiveness of the Border Patrol’s  efforts to reduce migrant deaths, we recommend that the Commissioner of  Customs and Border Protection assess the feasibility and cost- effectiveness of using multivariate statistical approaches to enhance  estimates of impacts of the initiatives.
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If you or your staff have any questions about this report, please contact me  at (202) 512-2758 or ekstrandl@gao.gov. Contact points for our Offices of  Congressional Relations and Public Affairs may be found on the last page  of this report. GAO staff who made key contributions to this report are  listed in appendix VI.
section_title: Appendix I: Objectives, Scope, and Methodology
paragraphs: This appendix describes our scope and methodology used in responding to  the three objectives addressed in this report: (1) How do the Border  Patrol’s data on trends in the numbers, locations, causes, and  characteristics of border-crossing deaths compare to other sources of data  on these types of deaths? (2) What differences, if any, are there in how the  Border Patrol has implemented the BSI methodology across its sectors?  (3) To what extent do existing data allow for an evaluation of the  effectiveness of the BSI and other Border Patrol efforts to prevent border- crossing deaths?
subsections: section_title: Methods to Determine the Reliability of Sources of Data on Border-Crossing Deaths
paragraphs: We assessed the reliability of BSI and NCHS data and reviewed the  methods used by CIR for identifying cases of border-crossing deaths in the  state vital registry data.
subsections: section_title: BSI Data
paragraphs: BSITS is a client-server database that serves as a central repository for  collecting, managing, and disseminating migrant incident data in support  of the BSI including the volume and types of rescues and the number and  types of migrant deaths that occur in each of the nine Southwest Border  Patrol sectors. Specifically, BSITS records the number of deaths and  rescues, followed by type, disposition, location (through GPS  coordinates), and information on the subject or victim. In order to ensure  data integrity, BSITS tracks record creation at the sector and user level.  The BSI does not allow records created outside the user’s sector to be  modified in BSITS. The system is monitored by a system security  administrator who monitors all user login and usage in order to maintain a  security audit trail. Access permissions to the system are managed by the  system security administrator through a security management tool, and  users may only log into the system using a secure user ID and password,  which is stored in encrypted binary format. Additionally, BSITS is subject  to a number of requirements that have been established for all sensitive  DHS automated data processing systems: it is required to develop internal  security procedures to restrict access of critical data items to only those  access types required by users; to develop audit procedures to meet  control, reporting, and retention period requirements for operational and  management reports; to allow for application audit trails to dynamically  audit retrieval access to designated critical data; to use standard tables for  requesting or validating data fields; to verify processes for additions,  deletions, or upgrades of critical data; and to be able to identify all audit  information by user identification, network terminal identification, date,  time, and data accessed or changed.
The Border Patrol provided us an electronic spreadsheet consisting of one  record, or entry, per incident in the BSITS database for all incidents,  including both rescues and deaths, recorded in the system from the  program’s inception in 1998 through December 21, 2005. In order to  protect the confidentiality of the information, the Border Patrol omitted  names from the data. In order to accurately interpret the data, we  reviewed definition tables provided by Border Patrol for each of the  variables in the database, system administration manuals, and a copy of  the query used to produce the data for our request. After completing  preliminary analysis of the data, we asked the Border Patrol to confirm the  number of subjects on which data was provided, to clarify the meaning  and values of several key fields in the database, and to provide additional  information about any missing or out of range values. To further assess the  reliability of the BSI data, we reviewed the written BSI methodology for  tracking and recording deaths for logic and consistency and interviewed  Border Patrol officials in Washington, D.C., as well as each of the nine BSI  sector coordinators in the field who have responsibility for implementing  the methodology and inputting data into BSITS. To determine the extent to  which the methodology has been implemented consistently across sectors  and over time, we asked officials about established methodologies for  tracking and recording deaths in BSITS, any changes to those  methodologies that may have occurred over time, and any methods Border  Patrol officials have used at both the national and local level to assess  whether the BSI methodology has been implemented fully and consistently  across sectors.
section_title: NCHS Data
paragraphs: NCHS collects and disseminates information on national vital statistics  through the National Vital Statistics System. The data are collected  through contracts between NCHS and vital registration systems operated  in the various jurisdictions responsible for the registration of vital events  including births, deaths, marriages, divorces, and fetal deaths. The  authority for the registration of these events resides individually with each  of the 50 states, 2 cities (Washington, D.C., and New York, N.Y.) and   5 territories (Puerto Rico, the Virgin Islands, Guam, American Samoa, and  the Commonwealth of the Northern Mariana Islands). The death certificate  is the source for state and national mortality statistics, and NCHS provides  standard forms for the collection of the data and model procedures to  ensure the uniform registration of deaths. NCHS also produces training  and instructional material as well as an automated mortality medical data  system for coding and classifying cause of death information from death  certificates. The NCHS data include records of all death certificates filed in  the United States regardless of the decedent’s country of origin. In order to  assure the objectivity of its statistical and analytic information products,  i.e., that they are accurate, reliable, and unbiased, NCHS obtains these  data through accepted statistical theory and practice. NCHS statistical and  analytic information products are derived using generally acceptable  statistical practices and methodologies, which enable responsible  statisticians and analysts outside NCHS to replicate the NCHS statistical  methods and obtain results consistent with those obtained by NCHS.  NCHS assures the security of its statistical and analytic information  products through the enforcement of rigorous controls that protect against  unauthorized access to the data, revision or corruption of the data, or  unauthorized use of the data. Some of the major controls used at NCHS  include access control, user authentication, encryption, access monitoring,  provision of unalterable electronic content, and audit trails. Dissemination  of data also follows generally recognized guidelines in terms of defining  acceptable standards regarding minimum response rates, maximum  standard errors, cell size suppression, quality of coding, and other  processing operations. NCHS also maintains staff expertise in areas such  as concept development, survey planning and design (including  questionnaire development and testing), data collection, data processing  and editing, data analysis, evaluation procedures, and methods of  dissemination.
We based our data request to NCHS on several key fields in the death  certificate including residence, birthplace, and cause of death in order to  identify likely cases of border-crossing deaths. The CDC Medical  Examiners and Coroner Handbook on Death Registration provides  detailed instructions on the registration of deaths and guidance on  completing the U.S. Standard Certificate of Death. According to the  handbook, the residence of a decedent (state, county, city, and street  address) is the place where the decedent’s household is located, the place  where the decedent actually resided, or where the decedent lived and slept  most of the time. If the decedent was not a resident of the United States,  the country of residence should be entered into the residence field of the  death certificate. If the decedent’s residence is not known, “unknown” is  entered into the residence field. The guidance also specifies that, for  decedents who were not born in the United States, the country of birth  should be entered into the death certificate, regardless of whether the  person was a U.S. citizen at the time of death. CDC’s specifications further  state that the underlying cause of death listed on the death certificate  should be the disease or injury that initiated the chain of events that led  directly and inevitably to death. The underlying cause of death is defined  as “the disease or injury which initiated the train of morbid events leading  directly to death, or the circumstances of the accident or violence which  produced the fatal injury.” Reported causes of death are then translated  into codes through a classification structure outlined in the International  Classification of Diseases (ICD) developed by the World Health  Organization. The ICD is used to classify diseases and other health  problems recorded on many types of health and vital records including  death certificates and hospital records. In 1999, a revision of the ICD was  implemented. The International Statistical Classification of Diseases and  Related Health Problems, Tenth Revision (ICD-10), established revised  codes for classifying mortality data and revised rules for selecting the  underlying cause of death.  ICD-10 replaced classification codes and rules  outlined in the previous version of the manual, the International  Classification of Diseases, Ninth Revision (ICD-9). The codes outlined in  the 9th revision (ICD-9) apply to all deaths registered between 1979 and  1998, while the 10th revision (ICD-10) applies to all deaths from 1999 to  the present.
In order to identify migrant deaths recorded in the NCHS main mortality  file—which contains records of all deaths occurring in the United States— we requested that NCHS provide us with aggregate, county-level data on  migrant border-crossing deaths by applying a set of specifications to the  data in the main mortality file. Our specifications included the following:   (1) a death must have occurred within 1 of the 45 counties in the BSI  target zone; (2) the death must have occurred in years beginning with 1990  and going through 2003, the most recent year for which NCHS data were  available at the time we did our work; and (3) deaths must be limited to  decedents who were foreign born, had a place of residence outside the  United States at the time of death, and died from one of the causes of  death that we associated with border-crossing deaths. We provided NCHS  a list of causes of death from the codes contained in the ICD codes— which, as described above, are used to classify the underlying cause of  death reported on the death certificate by public health officials such as  medical examiners and county coroners—and asked that NCHS officials  select those cases that matched one of the underlying causes of death on  our list. By requesting data over the period from 1990 to 2003, we  identified both ICD-9 and ICD-10 codes. We selected cause of death codes  that were associated with migrant border-crossing deaths used in the CIR  studies, the causes of migrant deaths identified by the Border Patrol, as  well as causes most commonly used by county medical examiners,  advocacy groups, and academic researchers. These include dehydration,  heat exposure, drowning, cold exposure, homicide, and traffic accidents  among others. Our data specifications also requested that NCHS provide  us with separate counts of decedents with unknown places of birth. NCHS  provided separate datasets for each year. The datasets also contained  counts of migrant deaths by age group and gender. After receiving the data  from NCHS, we reviewed the programming code as well as the statistical  output in order to verify that the results matched our initial specifications.
Because the place of residence listed on the death certificate is not  necessarily the same as the decedent’s home state, voting residence,  mailing residence, or legal residence, our counts of border-crossing deaths  may include some decedents who were either legal visitors or legal  residents of the United States but who were residing in another country  when they legally crossed the border and subsequently died. Additionally,  NCHS officials reported that if a body is discovered and the body is unable  to be identified, the person may be assumed to be a U.S. resident. As a  result, our counts may have excluded unidentified migrants who were  presumed to be U.S. residents by public health officials completing the  death certificate. Similarly, we requested that NCHS only provide data on  those cases where the underlying cause of death was a death commonly  associated with border-crossing. Focusing on the underlying cause of  death could result in undercounts of border-crossing deaths; cases could  be missed if the commonly associated causes are not reported when  appropriate or if they are reported incorrectly out of sequence. For  example, heat exhaustion may precipitate a heart attack. If heat  exhaustion is not reported at all or if it is not reported correctly as the  cause of the heart attack, then the heart attack would be coded as the  underlying cause, and the case would be excluded because the NCHS data  did not include heart attacks in the list of commonly associated causes of  border-crossing deaths. Alternatively, the NCHS data could also represent  an overcount of deaths if cause of death categories were defined too  broadly and resulted in the inclusion of deaths that were not directly  related to border-crossing.
In order to determine the reliability of the NCHS data for identifying  trends in deaths, we interviewed NCHS officials responsible for  maintaining vital registry mortality data and reviewed published NCHS  guidance on the completion of death certificates. We conducted interviews  with NCHS researchers, academic experts, and county medical examiners  familiar with the vital registry data about the data’s strengths and  limitations for accurately capturing data on border-crossing deaths. We  also reviewed NCHS documentation about the methods for collecting and  analyzing death certificate data in preparing the main mortality files.
section_title: CIR Data
paragraphs: In order to understand the methods and data compiled by CIR, we  conducted interviews with Karl Eschbach, the lead author of the studies,  about his methods for collecting and analyzing the data and also  conducted a GAO internal review of CIR methods.
section_title: Methods Used to Identify Trends in Federal Data on the Numbers, Locations, Causes, and Characteristics of Border-Crossing Deaths
paragraphs: We analyzed specific data elements in the BSI data that were relevant to  our analysis of border-crossing deaths. These included the number of  deaths, the types or causes of death—such as exposure to heat/cold,  motor vehicle accidents, drowning, and others—the location of deaths  including the county, sector, and GPS coordinates, and demographic  information on the decedent including age, gender, and country of origin.  We imported the data from the spreadsheet provided by the Border Patrol  into a statistical software package and analyzed counts of BSI-related  deaths by year, sector, and cause of death for fiscal years 1998 through  2005. Based on discussions with Border Patrol officials and the criteria  outlined in Border Patrol’s 2005 BSI Methodology Manual, we identified  border-crossing deaths as those deaths occurring within the 45 counties in  the BSI target zone and only included those entries designated by Border  Patrol as migrants who were in furtherance of an illegal entry at the time  of death. We also analyzed counts for characteristics of decedents  including gender and age.
Our analysis of the BSI data is based only on those deaths included in  BSITS as of December 21, 2005. We selected cases from fiscal year 1998  through fiscal year 2005 in which border-crossing deaths were recorded as  having occurred within one of the 45 counties in the BSI target zone while  the decedent was in the furtherance of an illegal entry into the United  States.  Our methodology is consistent with the BSI definition of a border- crossing death, but it differs from the methodology that Border Patrol uses  to calculate the total number of border-crossing deaths that occur each  year. According to Border Patrol officials, the Border Patrol generates its  reported annual death totals by selecting those cases recorded in the  BSITS database that occurred within any one of the Border Patrol stations  located within the BSI target zone or outside of the target zone if Border  Patrol was directly involved in the incident. In our analysis of the BSI data,  we only included deaths occurring within one of the 45 BSI counties and  did not select deaths that may have occurred outside of the target zone.   As a result, our total counts may not match the total numbers reported by  the Border Patrol.  Additionally, our sector-level counts of border-crossing  deaths may also differ from Border Patrol’s. Border Patrol classifies  deaths into sectors based on the Border Patrol station that recorded the  death. Using the criteria outlined in the 2005 BSI Methodology Manual, we  instead used data regarding the county in which the death occurred to  classify deaths into sectors. Furthermore, 3 of the 45 counties in the BSI  target zone straddle the dividing line between two different Border Patrol  sectors. In these cases, our analysis may have identified deaths in these  counties as occurring in one sector, while the Border Patrol’s reports may  have counted the deaths as occurring in another sector. These differences  in methods of classification primarily affect reported totals for the El  Centro and Yuma sectors.
subsections: section_title: Methods Used to Compare Border-Crossing Deaths to Deaths in the General Population
paragraphs: To understand how the distributions of causes of migrant border-crossing  deaths compare to the general population, we analyzed relevant BSI and  NCHS data on the numbers and causes of death. From NCHS we requested  aggregate, county-level datasets for the years from 1990 through 2003 of  the number of U.S. residents who died each year in the 45 counties in the  BSI target zone and the numbers who died from the causes of death we  used to identify border-crossing deaths. We followed procedures similar to  those we followed in requesting and obtaining the NCHS data on migrant  deaths. We also compared counts of U.S. resident deaths by year, sector,  and county, including the total numbers and causes of death with migrant  border-crossing deaths between 1990 and 2003.
section_title: Assessing Change in Risk Associated with Attempted Illegal Entries
paragraphs: To assess whether the apparent risk associated with migrant border- crossing deaths has changed over time, we compared data on border- crossing deaths to data on the estimated number of illegal entries reported  in a published study by Jeffrey Passel at the Pew Hispanic Center as well  as to data on the number of apprehensions recorded by Border Patrol.  Passel’s estimates are based upon the residual methodology. We used data  on apprehensions that the Border Patrol provided us. We calculated the  percentage change over the period from 1998 through 2004 in the  estimated number of undocumented entries, the number of apprehensions,  and the number of border-crossing deaths, and we compared these  percentage changes to determine if the change in the number of deaths  over this period exceeded the change in the estimated number of  undocumented entries and the number of apprehensions (see table 2).
section_title: Review of Models Used to Estimate the Number of Migrants Attempting to Cross the Border
paragraphs: Because data are not available on the actual number of migrants that  illegally attempt to cross the border in any given year, we used estimates  of the number of border-crossers or undocumented migrants that enter the  United States each year. We previously reported on some of the data  limitations involved in estimating the illegal immigrant population as well  as the strengths and weaknesses of the available methods for estimating  the flow of illegal migrants across the border. We reviewed a number of  models that have been developed in recent years by researchers and  academic experts working in the arena of immigration issues. We  conducted an analysis of each model and assessed the methods used by  each in order to draw a conclusion about the most reliable estimates of  illegal entries.
subsections: section_title: Residual Method
paragraphs: Robert Warren and Jeffrey Passel employ a method for estimating the  number of unauthorized migrants using both data from the decennial  Census and counts from alternate government sources, such as DHS. This  method counts the number of foreign born individuals in the United  States, as enumerated in the Census or the Current Population Survey  (CPS), and then subtracts the number who have become naturalized or  who are legal resident aliens, which was obtained from the alternate  government source. The difference should be the number of  undocumented aliens. Because this method involves subtraction, it is  sometimes called the “residual method.”
Using a method similar to this one, Passel estimated that there were   10.3 million unauthorized migrants in the United States in 2004. Using  annual applications of this method, he estimated that between 400,000 and  700,000 unauthorized migrants have entered the United States each year  since 1992.
A drawback to using this methodology for measuring the number of  unauthorized migrants at risk for border-crossing deaths is that Census  Bureau data, such as the CPS, only count migrants who have been in the  United States for a sufficient amount of time for government census takers  to locate them. Migrants who only come to the United States for a short  period of time and then return to their home country would be less likely  to be included in this count. Further, this methodology cannot be used to  measure different rates of crossing by sector since the migrants may live in  different areas from where they crossed the border. Ultimately, this  method would not only count those individuals who crossed the border  illegally, but also those individuals whose status changed from authorized  to unauthorized, due to a visa expiring, for example.
section_title: Apprehensions Data
paragraphs: An alternate method for estimating the total number of illegal border  crossings is to calculate entries based on the number of apprehensions  recorded by the Border Patrol. From 1994 through 2004, Border Patrol  records indicate that between 0.9 and 1.7 million migrants were  apprehended in the nine southwest Border Patrol sectors each year,  peaking in 2000. However, apprehensions are partially determined by the  level of Border Patrol enforcement activity. Therefore, even if the level of  migration remained the same, the number of apprehensions might  fluctuate if the level of enforcement changes. More specifically,  apprehensions are not a direct measure of successful undocumented  migration, but rather they are an indication of unsuccessful undocumented  migration.
Unlike the residual method, because the Border Patrol maintains records  of apprehensions by sector, this method can be used to estimate entries by  sector. Border Patrol data indicate that, from 1992 to the present, there  was a large shift in apprehensions from the San Diego Sector to the  Tucson Sector.
In addition, the number of apprehensions is not the same as the number of  apprehended migrants, since many migrants attempt to cross the border a  number of times until they are able to cross successfully. Katharine M.  Donato reports survey evidence that shows that many migrants will  continue to attempt to cross the border until they are able to get through  undetected.
section_title: Repeated Trials
paragraphs: Another method for estimating undocumented migration uses the number  of people who have been apprehended previously to translate  apprehensions into an estimate of the number of undocumented migrants  crossing into the country. A version of this method is employed by Thomas  J. Espenshade in his 1995 study examining the use of INS data to measure  the flow of undocumented migration. Espenshade shows that the ratio of  apprehensions and undocumented flow is equal to the odds of being  apprehended on any given attempt to enter the United States illegally. It  follows then that the flow of undocumented migrants can be calculated by  dividing the number of apprehensions by those odds. Espenshade  estimates that the estimated gross volume of undocumented migration  generally exceeded the level of apprehensions by 2.2 in the period  between 1977 and 1988. While this factor varies over time, Espenshade  concludes that the two series track each other well, as the linear  correlation between them is 0.90.
However, there are some questions about using Espenshade’s model to  estimate the current number of illegal crossings. For one, the specific  factor may be different today; Espenshade’s figures are based on  calculations over an 11-year period, beginning almost 30 years ago. As  noted previously, the geographic pattern of migration was much different  then, with a larger number of crossings occurring in the San Diego area,  whereas today a more significant number of crossings occur in the desert  area of Arizona. Moreover, Gordon Hanson and Antonio Spilimbergo have  empirically demonstrated that as the level of border security increases, a  greater number of unauthorized migrants will be apprehended. Either of  these factors—a differential pattern of crossing or an increased level of  Border Patrol enforcement—may affect the ability of the Border Patrol to  apprehend migrants, thus affecting the extent to which Espenshade’s  estimate of 2.2 crossings per apprehension can be accurately applied to  current circumstances.
In addition, a key assumption of Espenshade’s model is that migrants will  attempt to enter repeatedly until they are successful, even if all entries  were attempted within a single month. However, the plausibility of this  assumption is unclear; for example, it may not be reasonable to assume  that a migrant will attempt to cross the border as many as 7 times in a  given month. Additionally, there are a number of other factors that may  make the assumption even less plausible today than it was in the period of  Espenshade’s study. Border Patrol apprehension data indicate that  increasing numbers of migrants are attempting to cross in the Tucson  Sector. However, due to high temperatures and rugged terrain, the desert  is often more difficult for migrants to navigate than urban areas. As a  result, increasing numbers of migrants hire smugglers, or “coyotes,” to  help them cross. This is a large expense, and it is not clear that the coyotes  refund the money if the crossing is not successful. In addition, the Border  Patrol has started returning migrants to the interior of Mexico through the  IRP in order to deter repeat attempts. Given the amount of time it might  take a migrant to travel from the interior of the country back to the border,  it seems likely that a migrant would be able to make fewer attempted  crossings within a single month.
section_title: Methods to Determine the Extent to Which the BSI Can Be Evaluated
paragraphs: In order to determine the extent to which existing data allow for an  evaluation of the effectiveness of the BSI and related Border Patrol efforts,  we interviewed Border Patrol officials in Washington, D.C., about how  they measure the BSI including any information on established  performance goals and measures. We requested any available information  on BSI resources, personnel, and equipment in order to determine the  extent to which the Border Patrol tracks and records information on  resources in relation to established performance goals and measures. We  also reviewed a number of other federal data sources on the Border  Patrol’s program goals and outcome measures including documents  published by the Office of Management and Budget and CBP’s annual  budget submission. We reviewed and analyzed available information from  the Border Patrol on program outcomes including a study on the BSI  conducted in July 2004 that examined the efforts of the BSI to reduce the  overall number of migrant deaths, the effectiveness of individual  components of the BSI to deter crossings, and the effect of specially  trained BORSTAR units, as well as the Lateral Repatriation Program, on  the number of deaths.
subsections: section_title: The Border Safety Initiative: Evaluation, Assessment, and Recommendations
paragraphs: In an effort to better measure the impact of the BSI, the Border Patrol  commissioned researchers at Rutgers University to evaluate the efforts of  the program. As one of its objectives, the study examined the  effectiveness of specialized BORSTAR agents in reducing migrant deaths  when compared with Border Patrol line agents. BORSTAR agents are often  deployed to high-threat areas or areas more likely to have deaths and  rescues. Rather than attempt to estimate the effect of the BORSTAR  agents on the number of deaths in a sector where they are deployed, the  study estimates the effect of an agent’s BORSTAR training on whether an  intervention results in a death or a rescue of a migrant. The researchers  applied a multivariate logistic regression that corrects for the migrant’s  age, gender, and the number of accompanying migrants. Using existing  data provided by the Border Patrol, they found that the probability of a  death is 88 percent less when a BORSTAR agent responds, as opposed to a  non-BORSTAR Border Patrol agent.
The study’s findings present an argument for BORSTAR’s effectiveness. If  BORSTAR agents have training that allows them to better treat injuries, it  follows that more rescued migrants will survive. However, it is unclear  whether findings from this analysis can be used as an evaluation of the BSI  as a whole without additional research. BORSTAR agents are only one  component of the BSI with a total of 164 BORSTAR agents deployed in the  9 sectors along the southwest border as of October 2005. In order to  understand the effectiveness of the program as a whole, it would be  necessary to examine the impact of other components of the program  including the use of rescue beacons, the impact of the media campaign to  discourage migrants from attempting to cross the border illegally, and the  effectiveness of other non-BORSTAR Border Patrol agents that may rescue  migrants in need of assistance.
section_title: 2005 Report on the Interior Repatriation Program
paragraphs: In 2005, the Border Patrol issued a report on the outcomes of the Interior  Repatriation Program (IRP), an effort initiated as part of the ABCI. The  Border Patrol reports that the IRP was intended to break the ties between  migrants attempting to cross the border and the smuggling organizations  that move people across the border. Program participants are migrants  who are apprehended while attempting to illegally cross the border; the  IRP offers them the option to be voluntarily repatriated to their  hometown, rather than being returned to a land port of entry along the  border where they might be more likely to attempt to cross again. The  program claimed a number of successes including a decrease in the total  number of exposure related deaths between 2003 and 2004 in Arizona, as  well as a lower recidivism rate among program participants. However,  exposure related deaths in the Tucson and Yuma Sectors actually  increased between 2004 and 2005. While the Border Patrol claims that the  IRP was responsible for reducing the number of deaths in Arizona  between 2003 and 2004, they do not similarly tie the increase in deaths  between 2004 and 2005 to the program. Rather, Border Patrol officials  point out that increased desert temperatures and improved data collection  methods may have contributed to the increase in recorded deaths.  Similarly, they state that increased numbers of deployed BORSTAR agents  may have increased the likelihood that agents would find deceased  migrants in the course of their patrols. Factors discussed in this report  point out that changes in the number of deaths alone cannot serve as a  reliable indicator for the success of the BSI or the IRP. As the Border  Patrol correctly notes, any number of factors beyond the efforts of the  Border Patrol may affect the number of deaths from one year to the next.  Just as the increase in recorded deaths between 2004 and 2005 may have  been affected by any one of a number of factors including increased  temperatures, increased patrols, or improved data collection, the decline  in deaths between 2003 and 2004 may have also been affected by a number  of factors independent of the IRP. Similarly, the report points to the  decreased recidivism rate among program participants, noting that the  reentry rate was lower among program participants than illegal aliens that  were returned to land border ports of entry. However, currently  participation in the IRP is voluntary, and those migrants who elect to  participate may be less likely to attempt to cross the border again.  Conversely, those migrants who intend to continue to attempt to cross  until they are successful may be less likely to participate in the IRP.
section_title: Appendix II: Deaths by Sector
section_title: Appendix III: Causes of Death
section_title: Appendix IV: Causes of Death for U.S. Residents and Migrants within the BSI Target Zone
section_title: Appendix V: Comments from the Department of Homeland Security
section_title: Appendix VI: GAO Contacts and Staff Acknowledgments
subsections: section_title: GAO Contact
section_title: Acknowledgments
paragraphs: In addition to the contact named above, William J. Sabol,   Samantha Goodman, Benjamin Bolitzer, Chad M. Gorman,   David Alexander, Amy Bernstein, Frances Cook, Ignacio Yanes,   Jerry Seigler, Christopher Ferencik, and Stephen Rossman made key  contributions to this report.