Immigration policy has been an ongoing subject of congressional attention in recent years and a topic of concern for the U.S. public at large. Mexicans are by far the largest group of U.S. migrants, and about 1 in 10 Mexicans now live (legally or illegally) in the United States. Indeed, Mexico-U.S. migration represents the largest binational migration flow in the world. What does Mexico's prominence in the U.S. migration system mean for U.S. immigration policy? On one hand, it means that U.S. immigration policy, to varying degrees, primarily affects Mexicans and Mexico. Today's Mexico-U.S. migration flows and the Mexico-born population in the United States are the product of previous immigration policy decisions, as well as of the long and complex history of the U.S. and Mexican economies, labor markets, and demographics. On the other hand, it also means that Mexico remains at the center of today's immigration debate, even if sometimes only implicitly. Recognizing Mexico's status within the U.S. migration system focuses attention on how the U.S. immigration debate affects Mexico, and on how Mexico may affect certain migration outcomes. This report begins with an overview of Mexico-U.S. migration flows, and reviews the history of migration policies in both countries. The report then describes current demographics of Mexico-born persons in the United States and their recent dispersion to new U.S. destinations—factors that have helped shape the politics of U.S. immigration policy in recent years. The last section of the report discusses four major issues in the U.S. immigration debate: migration control and border security, the lawful permanent resident (LPR) visa system, temporary worker programs, and potential legalization programs for certain unauthorized aliens. For each of these issues, the report describes the impact of proposed reforms on Mexicans and raises questions about how Mexico may affect policy outcomes. Does Mexico support U.S. immigration policy goals? Should the United States and Mexico pursue more collaborative approaches to certain immigration issues? The report also examines a fifth, related policy issue: efforts to reduce emigration pressures within Mexico. Migration to the United States consists of three main groups of migrants: LPRs, temporary nonimmigrants, and unauthorized aliens. Within each of these categories, Mexicans represent the largest group of foreign born in the United States. Lawful permanent residents are foreign nationals who live lawfully and permanently in the United States, and they are typically eligible to apply for U.S. citizenship five years after receiving their visas. The Immigration and Nationality Act (INA) specifies a complex set of numerical limits and preference categories for permanent immigration reflecting the principles of family reunification, the admission of immigrants with needed skills, the protection of refugees, and diversity by country of origin. The INA prioritizes family-based immigration, making more than three times as many visas available in the family-based preference categories as in the employment-based categories. The INA does not set aside LPR visas for Mexico, but Mexicans are especially likely to take advantage of the law's family-friendly rules, with 122,686 Mexicans becoming LPRs as immediate relatives of U.S. citizens or family-sponsored immigrants in FY2010 (see Figure 1 ). Overall, 88% of Mexicans were admitted in one of the family categories in 2010, compared to 67% of all LPRs. The figures differ even more for the decade 2000-2009: 93% of Mexicans were family-based compared to 65% of all LPRs (see Appendix B ). Foreign nationals who are admitted to the United States for a temporary period of time and an expressed reason are known as nonimmigrants. There are 24 major nonimmigrant visa categories, commonly referred to by the letter and numeral that denotes their subsection in Section 101(a)(15) of the INA, including for example B-2 tourists, E-2 treaty investors, and F-1 foreign students. The nonimmigrant visa categories authorizing employment include the H-2A visa for agricultural guest workers, the H-2B visa for other lower-skilled seasonal or intermittent workers, the H-1B visa for temporary professional workers, the J-1 cultural exchange visa, the E visa for treaty traders and treaty investors, and the L visa for intra-company transferees. Temporary professional workers from Canada and Mexico also may enter under terms set by the North American Free Trade Agreement (NAFTA) on NAFTA professional (TN) visas. Mexico was the top sending county of temporary nonimmigrants in FY2010, making up 27.8% of all such entries. Aside from tourists and business visitors, the large majority of Mexican nonimmigrants enter as H-2A or H-2B low-skilled workers (see Figure 2 ). Mexico was one of 58 countries eligible to send H-2A and H-2B nonimmigrants (as of January 2012), and Mexicans accounted for 82.9% of such low-skilled nonimmigrant visas issued in 2010. Mexicans represent a small proportion of other legal nonimmigrants (also see Appendix C ). About 11.4 million unauthorized aliens from various countries were estimated to be in the United States in 2010, down from about 12.1 million in 2007. Between one-half and two-thirds of unauthorized aliens enter without inspection (by crossing the border between ports of entry or being smuggled through a port) or enter illegally by using fraudulent documents. The remainder enter legally as nonimmigrants but then remain past the visa expiration date (becoming visa overstayers) or otherwise violate the terms of their nonimmigrant visa. Of the 11.4 million, an estimated 6.7 million unauthorized Mexicans resided in the United States in 2010, meaning about 59% of the unauthorized population was from Mexico (see " Legal Status "). In recent years, the George W. Bush and Barack Obama Administrations, along with some Members of Congress, have favored "comprehensive immigration reform" (CIR) packages that would include reforms to the LPR and nonimmigrant visa systems to expand legal inflows, legalization for certain unauthorized aliens, and new migration control measures. Congress has considered a number of CIR bills and related proposals during this period, but none have been signed into law. Thus, legislative and administrative action during the last decade mainly has focused on new enforcement measures at the U.S.-Mexican border and within the United States; and a record number of unauthorized aliens have been removed in each year since 2003, with Mexicans accounting for almost three-quarters of all removals (see " Immigration Enforcement and Border Security "). This section describes how social, economic, and demographic factors in Mexico and the United States along with migration-related policies in both countries have produced four phases in the regional migration system: limited seasonal flows prior to World War II, the Bracero temporary worker program from 1942 to 1964, the emergence of a predominantly illegal system from 1965 through the 1980s, and the consolidation of that system along with increased family-based immigration since the 1990s. While seasonal migration by Mexican agricultural workers dates back to the 19 th century—and while most of California, Arizona, New Mexico, Texas, Nevada, Colorado, and Utah once belonged to Spain and later Mexico—large-scale permanent immigration from Mexico to the United States is a recent phenomenon, as Figure 3 illustrates. Mexican LPR immigrants exceeded 1 million in a decade for the first time in the 1980s (the darker bars in Figure 3 ) and Mexicans accounted for more than 15% of total LPR inflows for the first time in the 1990s (the line in Figure 3 ). The lighter bars in Figure 3 depict U.S. census data on the total Mexican-born population living in the United States, which include legal immigrants, temporary nonimmigrants, and unauthorized migrants. As the figure illustrates, fewer than 1 million Mexicans lived in the United States as recently as 1970. All of these Mexican migration and population trends increased markedly beginning around the 1970s, however, with legal immigration (LPR inflows) and the total Mexico-born population living in the United States both roughly doubling during each decade beginning in 1970. Even as growth rates slowed after 2000, the Mexico-born population in the United States climbed to 11.5 million people by 2009. In contrast with earlier periods, in which the migration system was dominated by short-term, seasonal, migration for agricultural work in the U.S. Southwest, Mexican migrants in the United States today are equally divided by gender; most live permanently in the United States; they work overwhelmingly in non-agricultural occupations (see Table 3 ); and they are dispersed throughout the entire country (see Figure 6 ). What explains the shift from relatively low immigration levels for the first two-thirds of the 20 th century to the rapid growth of Mexican migration since 1970? International migration is primarily a function of structural demographic, economic, and social forces. High birth rates and limited economic opportunities have been "push factors" that encouraged emigration from Mexico for most of this period; and plentiful employment opportunities, connections to family networks, and an aging population have been "pulls factors" within the United States—though all of these push and pull factors are in flux. How these structural forces translate into migration outcomes also depends on migration-related policies in both countries that encourage or discourage international migration and that afford aliens different legal statuses. Push and pull factors propelling Mexico-U.S. migration were relatively limited in the early 20 th century. Transportation and social networks linking Mexicans to the United States were poorly developed, and migrant farm workers had limited access to labor markets beyond the four southwest border states. Violence and economic dislocation during the Mexican Revolution (1910-1920) resulted in additional migration, but also created opportunities within Mexico during the 1920s. U.S. demand for migrant workers plunged during the Great Depression as unemployment rates climbed to 25% in 1933, and remained above 15% until 1940. With limited push-pull factors, agricultural employers lobbied to exempt Mexicans from tough overall immigration restrictions passed in 1917. Over the objection of labor advocates, Congress created the first U.S. guest worker program, allowing Mexican nonimmigrant admissions between 1917 and 1920, and then exempted Mexicans and other Western Hemisphere migrants from per-country immigration limits imposed on the rest of the world beginning in 1921. U.S. migration policy swung the other way in 1929, when tighter screening criteria for Mexican visa applicants produced a 75% reduction in LPR admissions. Hundreds of thousands of Mexicans and their U.S.-born children returned to Mexico during the Great Depression, including many who were deported. Mexico also discouraged emigration (i.e., migration to the United States) during this period, with a 1926 law requiring exiting workers to obtain permission from municipal authorities, and a series of public relations campaigns to discourage outflows and support return migration. As a result, the 1930s were the only decade in which net migration in the region flowed north to south. As the United States mobilized for World War II, agricultural employers demanded increased labor; but after a decade of limited inflows they struggled to recruit Mexican workers. Mexican officials continued to oppose new emigration, which they viewed as a drain on Mexican resources and—based on the experiences of earlier migrants—as a threat to workers' rights. U.S. officials viewed immigration through the lens of the war effort, including the need to strengthen U.S.-Mexican relations, and were deferential to Mexican concerns. Thus, the Franklin D. Roosevelt Administration initiated negotiations with Mexico for a bilateral guest worker program, which became known as the Bracero program (from the Spanish term for laborer). Under the resulting treaty, Mexican workers were guaranteed a minimum wage (unlike U.S. farm workers), health benefits, housing, and transportation expenses. The United States suspended the bilateral program in 1948, partly over objections to its labor-friendly provisions, but resumed it in 1951 when the Korean War prompted new fears of labor shortages. After the war, the United States demanded changes that weakened the program's labor protections. The Bracero program had a lasting impact on the Mexico-U.S. migration system. With nearly 50,000 farms employing more than 400,000 Mexicans a year at the program's peak in the late 1950s, strong constituencies on both sides of the border grew to favor labor flows. Both governments supported the program, including by developing a transportation infrastructure to move agricultural workers from the Mexican interior to the border region and beyond. The mid-1960s marked the beginning of the modern era of regional migration and the shift from a system of mostly temporary agricultural migration to one characterized by longer-term resettlement, greater geographic and labor market diversity, and a growing volume of flows. The Bracero program had issued 4.6 million visas by 1964, and so helped spark the transformation by fostering a new generation of migration-oriented Mexican workers, U.S. employers, and transnational labor recruiters. In its aftermath, a variety of national and global forces combined to hold down wages and to expand low-skilled employment opportunities in the United States, factors which created increased migration pulls. At the same time, high fertility rates in Mexico combined with an agricultural privatization program produced high levels of agricultural dislocation, rural-urban migration, and new job seekers in Mexico—factors which together resulted in stronger migration pushes as well. With the end of the Bracero program, these stronger migration pushes and pulls coincided with fewer legal pathways for Mexican workers to enter the United States. Although Mexicans were eligible for H-2 temporary worker visas, the Department of Labor rejected many H-2 petitions in an effort to protect U.S. workers, and few employers used the program. The watershed 1965 amendments to the INA (P.L. 89-236) imposed the first numeric limits on Western Hemisphere immigration and prohibited unskilled seasonal/temporary workers from receiving employment-based LPR visas, a provision that mainly affected migrants from Mexico. The 1965 amendments also increased the priority of visas for family-based LPRs, which became the main pathway for legal immigration from Mexico (see Figure 4 ). The convergence of growing migration push and pull factors and shrinking opportunities for legal low-skilled migration increased illegal migration from Mexico. The number of unauthorized aliens apprehended grew three-fold between 1965 and 1970, and the proportion of such aliens from Mexico increased from 50% to 80%. The imposition of numeric limits on permanent immigration produced a backlog of roughly 300,000 Mexican visa applicants by 1976, resulting in a two-and-a-half year wait for visas for qualified applicants. By 1979, an estimated 1.7 million unauthorized aliens resided in the United States, including 1.4 million from Mexico. The House Committee on the Judiciary held a series of hearings on illegal migration beginning in 1971, and both chambers considered bills during the 1970s to discourage illegal immigration by penalizing employers of illegal aliens, among other proposals. Congress examined the issue for 15 years and then passed the Immigration Reform and Control Act of 1986 (IRCA, P.L. 99-603 ), which combined employer sanctions with a pair of legalization programs for certain unauthorized aliens and a 50% increase in border patrol staffing, among other provisions. A total of about 2.6 million people eventually were legalized through IRCA, including about 2.1 million Mexican migrants (81%, see Figure 4 ). Push and pull factors on both sides of the border remained strong in the quarter-century after IRCA. Globalization exerted downward pressure on U.S. wages and the continued shift to lower-skilled production, driving up demand for foreign workers in new types of occupations and in regions far away from the U.S.-Mexican border. Mexico enjoyed periods of rapid economic development, but employment creation did not keep pace with population growth as children born during Mexico's baby boom of the 1960s and 1970s entered the workforce during the 1980s and 1990s; and many Mexicans continued to see emigration as the most viable path to higher wages. By the 1990s, social scientists described U.S. employers and Mexican workers as "structurally dependent" on migration, meaning that migration had become a core feature of the regional labor market, regardless of cyclical wage and employment trends. Congress responded to these trends by passing four additional laws focused on illegal migration in the decade after the 1986 IRCA, authorizing additional investments in border security, restricting migrants' access to welfare and other public benefits, and streamlining procedures to remove unauthorized aliens. Border enforcement and migration control received additional attention after the 9/11 attacks, with Congress passing five more laws related to immigration control in 2002-2006. Overall, U.S. spending on migration control and related activities increased from about $1.2 billion in 1986 to about $17.4 billion in FY2012. At the same time, immigration reforms sought to reduce low-skilled employment-based inflows. The Immigration Act of 1990 ( P.L. 101-649 ) and the Nicaraguan Adjustment and Central American Relief Act ( P.L. 105-100 , Title II) reduced the total number of low-skilled LPR visas from 29,000 to 5,000 per year. IRCA provided for an unlimited number of temporary agricultural workers through the H-2A visa program, but many employers considered the program too cumbersome to use, and fewer than 10,000 H-2A workers were admitted per year prior to the mid-1990s. The 1990 Immigration Act also reaffirmed the commitment to family reunification as the chief goal of U.S. immigration policy, and immigrants from Mexico have been the top beneficiaries of this policy. Section 101 of P.L. 101-649 raised the numerical limits on family-sponsored immigration by establishing an annual floor of at least 226,000 immigrants to be admitted within these categories. Section 102 exempted the spouses and children of LPRs ("second preference immigrants") from the INA's 7% per-country ceiling, a provision that mainly benefits Mexicans since few other countries approach the 7% limit, and Mexico is the only such country with a large number of second preference immigrants. And Section 112 set a special allotment of 55,000 visas each year from FY1992 through FY1994 for spouses and children of LPRs who had legalized through IRCA. Thus, during the first decade the 1990 act was in effect, Mexicans made up 37% of all second preference spouses and children and 70.5% of all spouses and minor children of LPRs who had legalized through IRCA. Overall, 52% of all second preference spouses and children of LPRs admitted during FY2000-FY2009 came from Mexico. Mexico lacked a cohesive migration policy for most of the post-Bracero period, and successive Mexican governments expressed little public concern about the number of Mexican citizens leaving for the United States without proper documents, often at great personal risk. Beginning in the late 1990s, however, increasing migrant deaths along the U.S.-Mexico border, the precarious situation of unauthorized Mexican migrants in the United States, and attention to human rights abuses of Central Americans in Mexico led the Mexican government to take a more active approach to migration issues, including by reforming its own migration policy and by engaging with the United States about U.S. immigration policy. The Administration of Mexican President Felipe Calderón and the Mexican Congress have taken significant steps to overhaul Mexico's migration policies. Previously, Mexico's immigration law, the General Population Act (GPA) of 1974, limited legal immigration and restricted the rights of foreigners in Mexico, with unauthorized migrants subject to criminal penalties. In 2008, the Mexican Congress reformed the GPA to decriminalize simple migration offenses, making unauthorized migrants subject to fines and deportation, but no longer subject to imprisonment. That year the Calderón government also announced a new strategy and authorized more than $200 million in new investments to improve security conditions, modernize customs and immigration facilities, and promote development in Mexico's southern border region (also see " Reducing Unauthorized Emigration from Mexico "). In 2010, Mexico passed a law increasing penalties for alien smuggling, particularly abuses committed by public officials. Mexico's recent migratory reform efforts likely hinge on how well the government implements a new version of the GPA that was unanimously approved by the Mexican Congress and signed by President Calderón in May 2011. Some of the main objectives of the law are (1) to guarantee the rights and protection of all migrants in Mexico; (2) to simplify Mexican immigration law in order to facilitate legal immigration; (3) to establish the principles of family reunification and humanitarian protection as key elements of the country's immigration policy; and (4) to concentrate immigration enforcement authority within the federal Interior Ministry in order to improve migration management and reduce abuses of migrants by public officials. The law guarantees that all migrants have access to education, justice, and healthcare services, and limits the time that unauthorized migrants may be held in detention centers to 15 working days. The law also gives legal status to special government "Beta Groups" that assist migrants in distress and establishes special procedures for how children and other vulnerable groups should be treated. Since the regulations for the new law are still being developed, its implications are not yet known. Despite U.S. enforcement efforts after 1986, Mexico-U.S. migration increased steadily in the 25 years after IRCA, with the total Mexico-born population growing from about 2.8 million in 1979 to about 11.5 million in 2009. Unauthorized migrants accounted for about 60% of the increase. Yet Mexican migration flows have declined since 2006, and recent data from multiple sources show a net rate of unauthorized migration fluctuating near zero, with some evidence that more Mexicans are leaving the United States than arriving, particularly unauthorized Mexicans. Researchers attribute this decline to the U.S. recession, stepped-up U.S. border security and interior enforcement, increasing abuses of migrants by smugglers and transnational criminal organizations, and expanding job opportunities in Mexico, among other factors. Some researchers also have found evidence that the high cost of crossing the border has encouraged some unauthorized migrants to remain in the United States for longer periods of time rather than returning to Mexico on a seasonal basis. In addition to these short-term factors, lower Mexican emigration rates also may be a function of long-term demographic trends, as Mexico's fertility rate has fallen from an average of 7.2 children per woman in 1960 to about 2.2 today. Thus, while emigration from Mexico may increase with U.S. economic growth, some analysts doubt that future flows will reach the high levels observed in recent years because many fewer Mexicans will enter the workforce and because Mexico is becoming an increasingly middle-class country. While total emigration flows have declined, there is some evidence of increased emigration by middle and upper class Mexicans, particularly from northern Mexico, in response to drug trafficking-related violence. One study in December 2010 estimated that 230,000 Mexicans had been displaced by violence, and that roughly half of them had moved to the United States. Media reports indicate that some Mexicans who feared that they could be victims of the violence have sought asylum in the United States. CRS analyzed several data sources that could reflect increased flows by people fleeing violence in Mexico and found ambiguous results. U.S. asylum and nonimmigrant visa data do not show increasing Mexican inflows in these categories between FY2005 (the year before the recent surge in trafficking-related violence) and FY2010. Yet there is some evidence of a growing number of "credible fear" claims during this period and of a higher approval rate for such claims, with most of the increase occurring in FY2010. Some middle and upper class Mexicans also may be entering through other legal channels not reflected in these data, including as LPRs. Another development that could cause an uptick in Mexico-U.S. migration is a severe drought that began in May 2011 and now affects more than half of Mexico. Subsistence farmers and indigenous communities in northern Mexico have been particularly hard hit, with 200,000 people reportedly fleeing their homes for feeding centers. Mexico has set aside $2.5 billion for drought relief, but it is not yet known whether the aid will prevent additional displacement from affected areas, or whether internal displacement will lead to international migration. The Mexico-born population in the United States accounted for about 29% of the total U.S. foreign-born population of 39.9 million in 2010. Recent foreign-born population growth has occurred as native-born population fertility levels have declined and the median age of the U.S. population has increased. Thus, while the foreign born represented 12.9% of the total U.S. population in 2010, they accounted for roughly 32% of total U.S. population growth since 2000, and almost all growth in the 25- to 54-year-old population. Partly for this reason, the foreign born are disproportionately likely to be in the labor force: 25.5 million foreign-born workers represented 16.3% of the civilian labor force in 2010; and 7.8 million Mexico-born workers represented 29% of the foreign-born labor force and 5% of the total U.S. labor force. Mexican migration to the United States has attracted the attention of Congress and the public not only because of its scale, but also because the Mexico-born population in the United States possess a different socioeconomic profile from most other foreign-born groups. On average, the Mexican born in the United States are more likely than other foreign born to be unauthorized; and compared to other foreign-born and native-born populations in the United States, Mexicans are younger, have lower education levels, are more likely to work in lower-skilled occupations, and have lower measures of economic well-being. Recent changes in the geography of Mexican migration to the United States have directed additional attention to these issues (see " Geographic Dispersion "). With respect to their legal status, the foreign born fall into three broad groups: naturalized citizens, legal noncitizens (which includes permanent and temporary residents), and unauthorized aliens. Table 1 shows that the legal profile of those born in Mexico differs markedly from that of the rest of the foreign-born population. While the majority (52%) of all foreign born are naturalized citizens, the majority of the Mexican born (55%) are unauthorized. Thus, Mexicans accounted for an estimated 6.5 million of the 11.2 million unauthorized aliens estimated to be living in the United States in 2010, or 58% of the total number of unauthorized aliens in the United States. Mexicans also differ from most other foreign born and U.S. born in their age distribution, which may have important economic implications. While about 24% of native-born citizens fall within the prime 25-44 working-age cohort, this proportion rises to 38% for foreign-born persons from countries other than Mexico and 50% for the Mexican born (see Figure 5 ). Mexicans' prime-age bulge is associated with small populations at both ends of the age scale: just 6% of Mexicans are older than 64 (compared to 13% of natives and 14% of other foreign born); and just 8% of Mexicans are younger than 18 (compared to 8% of other foreign born and 27% of natives). Differences at the low end of the age range mainly reflect high fertility among first generation immigrants and the relative youth of many second generation immigrants. The large proportion of the native-born population under age 18 is also a function of the children born to the large post-World War II "baby-boom" generation that is between the ages of 47 and 65 in 2012. Education is a critical yardstick by which immigrants are often measured and immigration policies evaluated; and higher education levels correlate positively with labor market participation, higher incomes, and other measures of well-being. Mexicans born in the United States possess lower average levels of education than most other migrants, with 60% lacking a high school diploma, compared to 20% for all other foreign born and 11% for the native-born population (see Table 2 ). At the other end of the education spectrum, just 6% of the Mexican born have at least a four-year college degree compared with 36% for all other foreign born and 28% for native born, though an increasing proportion of Mexicans have obtained bachelor's degrees in recent years (see " High-Skilled Mexican Migration "). Similar differences between the Mexican born and other foreign born exist with respect to English language proficiency (see Table 2 ), another factor associated with positive labor market outcomes and social and cultural integration. Only half of the Mexican born describe their English speaking ability as proficient compared to more than four-fifths of other foreign-born persons. English proficiency is much higher (72%) among Mexicans younger than age 25 (as well as other migrants, 90%), largely as a result of being enrolled in U.S. schools. Legal status, age, educational attainment, and English proficiency all contribute to economic outcomes such as occupational attainment. Table 3 presents a broad occupational distribution for Mexicans, other foreign born, and U.S. natives. The Mexico-born labor force is concentrated in industries characterized by low-skilled employment, such as construction, cleaning, food preparation, and agriculture. In contrast, all other foreign born have similar distributions as the native born and are more concentrated in sales, business, and scientific occupations. Type of occupation correlates with economic well-being. Table 4 shows that the Mexican born have lower median personal incomes, greater poverty, smaller proportions covered by health insurance, and fewer people owning their own homes. In contrast, all other foreign born resemble the native born relatively closely on the first three measures, and have a proportion of homeowners (58%) roughly midway between the Mexican born (46%) and the native born (69%). In summary, the Mexican born residing in the United States possess a distinct demographic profile compared to most other foreign born: they are more likely to lack legal status (55% compared to 17%), to be of prime working age (50% compared to 38%), and to lack a high school diploma (60% compared to 20%) and English proficiency (51% compared to 80%). This profile helps explain why the Mexican born concentrate more heavily in lower-skilled, lower-paid occupations and measure lower on key indicators of economic well-being. The contrasting profiles between the Mexican born, other foreign born, and native born have contributed to debates about the size and character of immigration flows. Mexican migration has also attracted attention in recent years because of the geographic dispersion of Mexican migrants to new U.S. regions and destinations, increasing the visibility of Mexican migration beyond traditional southwestern and selected urban settlement areas. As Figure 6 illustrates, states in the Southwest have the highest proportion of Mexican born, but states in the South and Midwest have experienced the greatest proportional increases in their Mexico-born populations over the past two decades (see Appendix A for greater detail). Several states and localities with high levels of Mexican migration and/or rapid growth of Mexican migration have passed immigration-related legislation in recent years. Immigration policy has been a subject of congressional concern over many decades. Since 2001, Congress has considered a range of measures to strengthen border security and migration control, changes to the LPR and nonimmigrant visa systems, and proposals to legalize certain unauthorized aliens, among other issues. Mexico's status as the largest source of U.S. migrants and as a continental neighbor means that many U.S. policies primarily affect Mexicans. Viewing the immigration debate from a U.S.-Mexico perspective raises a number of questions about each of these issues, including about Mexico's role in shaping U.S. migration flows and steps Mexico has taken and could take to reduce unauthorized migration. The United States and Mexico have several common interests in a well-functioning migration system. First and foremost, both countries benefit from a secure border that permits safe and orderly migration and commerce, limits illegal flows, protects public safety and human rights, and disrupts criminal enterprises. Second, with Mexico being the United States' third-largest trading partner in 2012 and migrant remittances being among Mexico's largest sources of foreign exchange earnings, regional migration issues are inextricably linked to both countries' economic well-being. Third, both countries have benefitted from demographic complementarities, with Mexico's post-1960 baby boom helping to sustain U.S. population growth in recent decades as the U.S. population has aged. These common interests have, at times, led the United States and Mexico to approach migration from a bilateral perspective, as they did through the Bracero program (see " 1942-1964: The Bracero Program "). More recently, President George W. Bush and Mexican President Vicente Fox reached a framework agreement to pursue a major bilateral migration deal. Under the agreement, announced on September 6, 2001, the two presidents outlined a bilateral approach to migration reform that would combine a new Mexico-U.S. guest worker program, legalization for most unauthorized Mexican migrants in the United States, enhanced border enforcement including steps by Mexico to discourage illegal outflows, and increased U.S. investment to create alternatives to emigration in Mexican migrant-sending communities. Although the migration talks fell off the bilateral agenda after the 9/11 attacks, the pillars of the framework agreement remained at the center of the U.S. immigration debate. At the same time, migration has also been a source of bilateral tension. Some people are concerned about the impact of low-skilled immigration on the U.S. economy and about illegal migration, and many Mexican migrants fall into these categories (see " Mexicans in the United States "). Conversely, while Mexico recognizes U.S. authority to make and enforce immigration laws—just as Mexico enforces its own migration laws—Mexico also seeks to protect the rights of its nationals abroad. This perspective has led to episodic disagreements over U.S. immigration policy and policy enforcement. Immigration enforcement and border security are at the heart of the immigration debate, including questions about how to prevent or deter illegal migration across the U.S.-Mexican border and the removal of unauthorized migrants and certain other aliens from within the United States. Under an internal INS planning document developed in 1994 and a U.S. Border Patrol national plan published in 2005, U.S. border enforcement during the last two decades has been organized around a strategy of "prevention through deterrence," an approach that places enhanced personnel, fencing, and surveillance technology along heavily trafficked stretches of the border. The border patrol's strategy has been designed to discourage aliens from entering the United States at traditional illegal crossing points and to funnel illegal crossers to ports of entry (POEs), where they are subject to inspection by U.S. Customs and Border Protection (CBP) officers, or to remote areas, where difficult terrain and the absence of a transportation infrastructure give border patrol agents a tactical advantage in apprehending illegal crossers. This approach has resulted in substantial enforcement resources at the U.S.-Mexican border. Since the strategy was initiated beginning in FY1994 through FY2011, the number of border patrol agents posted on the Southwest border has increased from 3,747 to 18,506; the United States has installed fencing along 651 miles of the border; and over $1 billion has been spent to develop an integrated border surveillance system, with mixed results. In addition, Presidents George W. Bush and Obama both ordered National Guard troops to be deployed to the U.S.-Mexican border, and six unmanned aircraft systems now operate there. Since 2005, a second key feature of border enforcement has been a policy CBP describes as its "consequence delivery system." Whereas immigration agents historically returned most aliens apprehended at the U.S.-Mexican border to Mexico with minimal processing, an increasing proportion of such aliens now are subject to formal removal, face immigration-related criminal charges, or are repatriated to Mexico at a remote location rather than the nearest POE (also see " Efforts to Reduce Illegal Migrant Recidivism "). The goal of these enhanced consequences is to raise the costs to aliens of being apprehended and to make it more difficult for them to reconnect with smugglers in Mexico following a failed entry attempt. The United States also conducts interior immigration enforcement, with U.S. Customs and Immigration Enforcement (ICE) taking the lead on efforts to identify, detain, and remove unauthorized migrants and certain other aliens from within the United States. Certain U.S. states and localities also have passed migration control measures of their own, though the Obama Administration has filed suit to block several such laws, with Mexico filing amicus curiae (friend of the court) briefs in some of the cases. The Supreme Court is expected to rule on the constitutionality of key state immigration enforcement measures in 2012. As Figure 7 illustrates, Mexicans account for the vast majority of deportable and removable aliens apprehended since 1991 (the orange bars in the figure): 427,940 out of 516,992 aliens apprehended in FY2010 (83%), and 23.1 million out of 24.8 million apprehended overall during this period (93%). Similarly, Mexicans accounted for 282,003 out of 387,242 aliens formally removed in FY2012 (73%, the blue bars in the figure) and 2.7 million out of 3.7 million aliens formally removed overall during this period (72%)—even higher proportions than their estimated share of unauthorized migrants within the United States. The United States has invested considerable resources in personnel, fencing, and other border enforcement tools over the last two decades. By some measures, these investments may have begun to have paid off, as apprehensions of unauthorized migrants reached a 42-year low in 2011 and crime rates in U.S. border cities were below the national average. Thus, the Obama Administration has described the border as more secure than ever, and the Administration has proposed no major increases in border spending for FY2012-FY2013. Similarly, while U.S. Border Patrol (USBP) national strategies published in 1996 and 2004 proposed substantial new investments at the border, its forthcoming strategic plan mainly proposes, instead, to reallocate existing resources along the border in response to changing threats. Yet some people question whether the border is truly secure, especially in light of high rates of drug trafficking-related violence on the Mexican side of the border. The recent drop in apprehensions may primarily reflect changing push-pull factors, including the U.S. economic downturn, robust economic growth in Mexico, and Mexico's lower birthrate, rather than successful border enforcement. Will unauthorized migration increase as the U.S. economy recovers or if Mexico experiences a downturn of its own? In light of these concerns, some Members of Congress have called for greater investments in border fencing and personnel, including a greater role for the National Guard in border enforcement. Questions about how to enforce the border have additional implications when viewed from a bilateral perspective. Border fencing and the U.S. policy of prevention through deterrence have been controversial in Mexico because some people believe that enhanced border enforcement has resulted in a rising death toll among unauthorized border crossers, because of the negative symbolism of a "border wall," and because of the effects of fencing and surveillance infrastructure on the sensitive border ecosystem. Enhanced enforcement also may have contributed to higher fees charged by Mexican smugglers and to stronger connections between human trafficking and other types of smuggling, though the relationship between migration, crime, and violence is complex, and the impact of migration enforcement on these factors is unknown. Given the large number of unauthorized Mexicans in the United States, some people believe that Mexico bears some responsibility for illegal flows and should play a greater role in migration control. Mexico currently supports U.S. migration enforcement in two main ways. First, Mexico's National Migration Institute (INM) within the Secretariat of the Interior combats transmigration by unauthorized migrants crossing Mexico bound for the United States. As Figure 8 indicates, the estimated number of illegal Central American transmigrants increased from about 236,000 in 2000 to a high point of about 433,000 in 2005 before falling back to about 140,000 in 2010. INM detained and deported slightly more than half of these migrants between 2001 and 2010. Second, Mexican and U.S. law enforcement agencies collaborate to combat alien smuggling and human trafficking, along with other transnational criminal activities. CBP's International Liaison Unit (ILU) maintains regular contact with Mexican law enforcement agencies to share information about border area crime and to coordinate responses when agents confront border-area violence. U.S. Border Patrol sector chiefs and Mexican Interior Ministry officers co-chair monthly meetings among border-area law enforcement agencies. U.S. and Mexican law enforcement agencies cooperate through the ICE Border Enforcement Security Task Force (BEST) program, initiated in 2006 to combat drug and human smuggling. ICE's Transnational Criminal Investigative Unit in Mexico City works with Mexican Federal Police and Customs Officials to combat high-risk human smuggling. U.S. and Mexican law enforcement agencies also collaborate to prosecute smugglers through the Operation Against Smuggling Initiative on Safety and Security (OASISS), a bilateral program that enables Mexican alien smugglers apprehended in the United States to be prosecuted in Mexico. From the time of its inception in 2005 through the end of FY2011, OASISS referred 2,617 cases to Mexican authorities. Mexican and bilateral investigations and prosecutions against human trafficking have intensified since Mexico reformed its federal criminal procedure code to criminalize trafficking in late 2007. Since that time, all of Mexico's states have enacted code reforms that criminalize at least some forms of human trafficking. Since 2007, the State Department has removed Mexico from its human trafficking watch list and ranked Mexico as a "Tier 2" country (i.e., the second-best out of four categories) in its annual Trafficking in Person s (TIP) reports, reflecting this progress. In 2011, President Calderón proposed a series of constitutional reforms that would require those accused of trafficking to be held in prison during their trials and guarantee the anonymity of victims involved in TIP cases. The Mexican Congress recently approved a new law against trafficking that amends the 2007 federal anti-TIP law and includes prison sentences of up to 40 years for people convicted of sexual exploitation. Yet the Mexican Congress also cut funding for anti-TIP efforts and for the Attorney General's Office in the 2012 budget, which could weaken Mexico's ability to prosecute TIP cases. Most Mexican law enforcement activities with respect to illegal migration and transnational crime receive some degree of U.S. financial support. One way to increase Mexico's role in migration enforcement may be for Congress to consider additional investments in these programs. The United States also could include migration control as an explicit priority within other existing programs, such as the Mérida Initiative, which focuses on combating drug trafficking-related organized crime. On the other hand, Mexico is already among the largest recipients of U.S. anti-TIP assistance in the Western Hemisphere, and some Members of Congress may be reluctant to invest more resources in such programs. In addition, given ongoing concerns about corruption in Mexico, U.S. law enforcement agencies may prefer to carry out their own investigations, and Congress may prefer to emphasize unilateral enforcement policies. Although the numbers have dropped since 2007, hundreds of thousands of aliens are repatriated to Mexico each year. What happens when aliens are repatriated to Mexico, and what can be done to promote migrants' successful re-integration and to minimize repeat entries (i.e., "recidivism") among illegal migrants? Under a 2009 agreement with the Mexican Foreign Ministry, ICE and CBP administer repatriations to Mexico in accordance with a standard template, with operational details arranged at the local level between CBP and Mexican Consular and INM officials. The arrangements allow for most Mexicans to be repatriated to the Mexican POE closest to the point of apprehension and in a manner consistent with mutual hours of operation and staffing availability. Four groups of Mexicans receive special treatment during the repatriation process: Unaccompanied minors must be repatriated during daylight hours, and the United States works with Mexican consular officials and other agencies to transfer unaccompanied minors to appropriate child welfare representatives in Mexico. The Mexican Interior Repatriation Program (MIRP) is a voluntary program established in 2003 to allow certain unauthorized aliens apprehended in Arizona during the summer months to fly to Mexico City and take a bus to their communities of origin, rather than being returned to the border. The MIRP is designed to prevent migrant deaths in the desert, to remove deportees from precarious conditions in northern border cities, and to reduce recidivism. About 125,000 individuals participated in the Interior Repatriation Program between 2004 and 2011, with the United States covering most program expenses. The countries announced plans in February 2012 to expand the interior repatriation program to other regions of the border beginning in 2012. The Alien Transfer Exit Program (ATEP) is part of CBP's Consequence Delivery System. Under ATEP, certain Mexicans are removed to locations hundreds of miles away from the point of apprehension—typically involving the movement of people apprehended in Arizona to POEs in Texas or California. CBP sees the program as a way to disrupt migrant smuggling networks and discourage recidivism, but the program is controversial in Mexico because persons repatriated through ATEP may find themselves effectively stranded in border communities without resources to find employment or to return home. In cases involving serious criminal aliens, ICE has responded to a request from Mexico to remove certain people apprehended near El Paso, TX, to locations other than Mexico's Ciudad Juárez in order to avoid exacerbating high levels of violence there. As security conditions in other border cities have deteriorated, however, it has become increasingly difficult for U.S. and Mexican officials to find places to send criminals, particularly those with felony convictions. In addition, whereas ICE historically provided limited biographical information to INM officials regarding criminal (and non-criminal) aliens removed to Mexico, under a 2010 agreement DHS shares criminal histories with Mexico about Mexicans who have been convicted of certain serious felonies in the United States and are being removed to Mexico. Under a pilot program at the Calexico POE, DHS provides the Mexican Federal Police with information about serious criminal aliens 24 hours prior to their removal. Whether these programs succeed in reducing recidivism among illegal migrants is unknown, though CBP has recently begun collecting data to allow it to evaluate how the MIRP, ATEP, and other enforcement programs affect recidivism. To the extent that these programs are viewed as successful, and to the extent that coordination and information sharing about serious criminals aids Mexican efforts to reduce violence in the border region, Congress could consider providing direct funding for these programs, and DHS could expand them. On the other hand, some may oppose certain information sharing due to privacy concerns, and ATEP and MIRP are both more expensive than standard repatriation procedures. Congress also could support Mexican programs to promote the successful reintegration of people repatriated to Mexico. In December 2007, President Felipe Calderón inaugurated a program for deportees called Programa de Repatriación Humana (Humane Repatriation Program or PRH). The program began in Tijuana and has since expanded to nine locations along the U.S.-Mexico border, assisting 267,317 migrants in 2010—roughly 60% of people returned that year. Although PRH does not have a programmatic budget, it works with non-governmental organizations, the private sector, and local and federal government officials to ensure that migrants receive information on where they have been deported, food, a phone call to relatives, medical attention, shelter, and local transport. Special attention is provided to unaccompanied minors and other vulnerable groups. Expanded services—job training, employment referrals, and micro-enterprise loans—have recently been offered to migrants in Ciudad Juárez through a municipal partnership with the International Organization for Migration (IOM). These types of services have been offered by IOM to returning migrants in other countries, often funded by countries from which the migrants have been returned, including the United States. To the extent that these programs promote successful reintegration for returning migrants and reduce recidivism, they also may merit additional U.S. support. The Illegal Immigration Reform and Immigrant Responsibility Act of 1996 ( P.L. 104-208 Div. C), as amended, requires DHS to develop and implement a comprehensive biometric system to record the entry and exit of every alien arriving in and departing from the United States. The U.S. Visitor and Immigrant Status Indicator Technology (US-VISIT) System, which manages entry-exit data, is operational at all U.S. POEs. But many visitors are exempted from the US-VISIT system, including most Mexicans entering the United States with border crossing cards (BCCs, or "laser visas"), who account for the majority of Mexican admissions to the United States. In addition, while CBP collects biographic data (i.e., names, addresses, document numbers, and other identifying information) from persons departing the United States by air and sea, it does not collect any data from people exiting the United States through land POEs on the U.S.-Canadian or U.S.-Mexican borders. Some Members of Congress have urged DHS to implement a full entry-exit tracking system. The primary obstacles to more complete entry-exit tracking are limited infrastructure and staffing. Mexicans with multiple-use BCCs are exempted from the US-VISIT system because to require them to provide fingerprints each time they enter the United States would result in longer wait times for all visitors. The challenges are even greater on the exit side because existing POEs were not designed to include exit processing, so CBP would have to reconfigure ports to create exit lanes and shift personnel away from entry lanes in order to begin collecting exit data. The United States and Canada have proposed a potential solution to the exit infrastructure problem on the northern border which also could serve as a model for the U.S.-Mexican border: an integrated entry-exit system. Under the U.S.-Canadian proposal, the record of a land entry in Canada could be utilized to establish an exit record from the United States (and vice versa). An integrated entry-exit system would not require new infrastructure because all travelers to Canada already must be inspected and admitted by Canadian immigration officials. Pilot projects to test integrated entry-exit on the U.S.-Canadian border are expected to begin in 2012. The United States and Mexico could consider a similar integrated system at southwest border land ports, especially if the U.S.-Canadian project is deemed successful. On one hand, an integrated entry-exit system may offer a solution to the challenge of tracking land exits given the limited infrastructure for tracking land exits. On the other hand, Mexico currently does not screen 100% of land entries (in contrast with Canada), and establishing an integrated entry-exit system likely would require construction of additional inspection lanes in Mexico. Some people also may question the integrity of Mexican border officials or identification technology, and whether an integrated system would be as reliable as one based fully in the United States. The Mexico case exemplifies two tensions in U.S. permanent immigration policy. First, family reunification has always played an important role in U.S. immigration law, but some people believe the system is unbalanced, and places too great an emphasis on family immigration at the expense of employment-based flows. While about 65% of all permanent immigrants to the United States from 2000 to 2009 were admitted on the basis of family connections, the proportion rises to 93% for Mexican immigrants (see Appendix B ). Second, while the United States admits about 1 million LPRs per year, millions more wait in the approved visa backlog: that is, the "queue" of people whose visa applications have been approved by DHS but for whom the State Department has not made a visa available due to overall and per-country numeric limits. Depending on their nationality and visa category, some people may wait in the visa queue for years or even decades. As of November 1, 2011, the backlog of Mexican visa applicants with approved LPR petitions totaled 1.4 million people, or about 30% of the 4.5 million people worldwide with pending petitions (see Table 5 ). The overwhelming majority (97%) of the these approved petitions are for family-based LPRs, and the proportion is even higher (99%) for approved Mexican petitions. Mexico is the leading country within each of the family-based visa queues, and Mexican petitions account for over 40% of approved petitions for spouses and children of LPRs. Several legislative proposals introduced during the last decade would have shifted the balance between family- and employment-based flows and/or reduced visa backlogs: Some have proposed changes to the LPR system to reallocate some family-based visas into employment-based categories. A 2007 Senate bill would have accomplished this change by adopting a Canadian-style points-based system favoring immigrants with particular job skills. Other have proposed eliminating one of the family-based preference categories, such as siblings of U.S. citizens. Some have proposed placing the spouses and minor children of LPRs (i.e., certain second preference family-based immigrants) in the same category as immediate relatives of U.S. citizens, and so exempting them from numeric limits. Reclassifying such immigrants as immediate relatives would ease family backlogs but likely would result in a higher proportion of LPR visas going to family members. Some have proposed raising or eliminating the per-country ceiling on certain types of LPRs. A bill passed by the House in 2011, for example, would eliminate the per-country ceiling on employment-based LPR admissions, and would raise the per-country ceiling on family-based admissions from 7% to 15%. Any change to LPR visa rules would have a disproportionate impact on Mexicans. In general, changes to shift visas from family- to employment-based categories would reduce the number of visas available to Mexicans. Conversely, given the high proportion of Mexicans in the family-based visa queue, Mexicans would be the primary beneficiaries of proposals to reclassify family members of LPRs as immediate relatives. While the 2011 proposal to raise per-country ceilings mainly is designed to address employment-based visa backlogs among professional and skilled immigrants from India and China, the bill's inclusion of a higher per-country ceiling on family-based immigration means that it also would result in increased Mexican inflows. Some argue that the LPR system should make more visas available for Mexicans. Long waiting lists for people with approved petitions divide families, and may be a factor in the decision by some family members to migrate illegally. Some employers may hire unauthorized Mexican (and other) workers, in part, because they cannot hire an employment-based LPR immigrant in a timely manner. Thus, more Mexican LPR visas could result in less unauthorized migration. There is historical precedent for providing Mexicans with special treatment under U.S. immigration law (see " History of Mexico-U.S. Migration and Policies "). Mexicans were exempted from certain grounds for inadmissibility during World War I; Mexicans (and other Western Hemisphere immigrants) were not subject to numeric limits like Europeans and other Eastern Hemisphere immigrants after 1921; and Mexicans had privileged status under the Bracero program. Even after imposing the per-country ceiling in 1965, Congress considered several bills to raise Mexico's immigration quota; and Mexicans were the main beneficiaries of special visa categories created in 1976 (for "non-preference immigrants"), 1986 (IRCA's legalization provisions), and 1990 (for relatives of LPRs who had legalized through IRCA). On the other hand, generating more LPR visas for Mexico would require either an increase in total immigration levels or a reduction in visas for some other country. Either of these options may face opposition from various constituencies. To raise the LPR visa ceiling for Mexico and not other countries would cut strongly against the norm of universality that was at the heart of reforms to the INA passed in 1965. Some people also would oppose increasing the number of low-skilled immigrants entering the United States, the demographic most common among Mexican immigrants. According the U.S. Department of State Visa Office, 84% of Mexican nationals who were issued a temporary visa (excluding short-term B1/B2 visas) in FY2010 received H visas for temporary workers. Mexicans made up 92% of 40,330 H-2A workers and 71% of 40,671 H-2B workers in 2010. As Figure 9 shows, even after a decline during the recent economic downturn, the number of Mexicans receiving temporary work visas increased 253% between 1997 and 2010, with the vast majority in low-skilled categories. Congress has considered a number of proposals in recent years to facilitate the admission of high-skilled workers to the United States. With several categories of Mexican nonimmigrant visas not subject to numerical limits, including the North American Free Trade Act (NAFTA) TN visa for professional workers, the existing system already includes opportunities for additional temporary educational and employment migration from Mexico. As an increasing proportion of Mexicans obtain a bachelor's degree or higher, more may qualify for professional and cultural exchange visas, and Mexico may be a ready source of high-skilled labor for the United States. The most promising avenue for high-skilled circular migration may be in the areas of science, technology, engineering, and mathematics (STEM) fields. A 2011 multi-country survey of 4,800 students from around the globe found that 69% of Mexican students planned to pursue a STEM education—the highest proportion of any country in the survey. Yet while the United States remains the leading host country for international students in STEM fields, Mexico is not among the top 10 sending countries of foreign graduate students pursuing U.S. STEM degrees. Increasing the number of Mexicans obtaining STEM degrees at U.S. universities may prompt U.S. employers to hire more Mexicans with TN or H-1B visas, and return migration by high-skilled Mexicans may make Mexico's economy more competitive. Yet high emigration levels among talented and educated persons from Mexico also may hinder economic development there, especially if a large proportion of such visitors eventually remain in the United States. Some people who oppose increased permanent migration from Mexico may favor a bilateral temporary worker program. Large-scale low-skilled temporary worker programs have been a part of most CIR bills since 2006, and a new temporary worker program for agricultural workers was proposed in the House in 2011. If a low-skilled temporary worker program is created or expanded, should it set aside certain visas for Mexican workers? Although legislative proposals during the last decade have not focused on a Mexico-specific temporary worker program, the Bracero program offers a historical precedent. President George W. Bush also proposed a Mexico-specific program as part of his framework agreement with President Fox in 2001, and the TN visa sets a present-day precedent for a bilateral program with Mexico. A temporary worker program could be designed to target sectors of the U.S. economy in which employers may struggle to recruit legal workers, particularly sectors in which Mexicans are concentrated (see Table 3 ), and so could address the "jobs magnet" that drives much unauthorized migration to the United States. Some people see the "circular migration" that dominated the Mexico-U.S. migration system prior to the 1980s as a good model, with many Mexicans spending short periods of time in the United States, and then returning to Mexico with new job skills and money to invest in their home communities, rather than settling (often illegally) in the United States. Although the Bracero program offers a cautionary tale, numerous countries have established broadly similar bilateral guest worker programs in recent decades. Some observers consider government-to-government agreements such as Canada's temporary agricultural visa for Mexican workers as a "best-practice model" because they give countries of origin a role in selecting workers, overseeing contract enforcement, and supervising return migration. Mexico also could be involved in additional aspects of a bilateral temporary worker program, such as managing temporary workers' health care expenses and/or their retirement savings. On the other hand, the arguments that ended the Bracero program in the 1960s also remain salient today. From this perspective, visas for temporary workers who are low-skilled or unskilled—regardless of their country of origin—are likely to depress domestic wages and working conditions unless there are strong worker protections. Any temporary worker program confronts a tension over how to enforce such protections without discouraging employer participation. Perhaps most importantly, the markets for visas may not follow the same logic of supply and demand as other types of commodities: more low-skilled visas may encourage increased migration overall, rather than shifting workers from unauthorized to legal channels. Even people who are sympathetic to U.S. employers' requests for such workers point out that the current level of unemployment in the United States does not bode well for increasing low-skilled migration. A variety of proposals have been put forth over the past decade to enable certain unauthorized resident aliens to qualify for an adjustment to LPR status. Many of these options would establish new mechanisms or pathways, with Mexicans being among the largest group of beneficiaries of most such proposals. The experience of IRCA has cast a shadow on these debates: while some people view the 1986 law as a partial success for having helped weave millions of previously unauthorized aliens into the fabric of the United States, others oppose legalization, and IRCA ultimately failed to fulfill one of its primary goals: to stop the flow of illegal migration. Given the sheer number of unauthorized Mexicans living in the United States, some maintain that Mexico should be involved in a discussion about how to structure a possible legalization program. Whether such a program would provide unauthorized aliens the opportunity for LPR status or for a temporary visa would have an impact on Mexico's demography and economy. The handling of those aliens deemed ineligible for legalization could also benefit from a bilateral agreement. For example, Mexico could assist with the identification of unauthorized Mexicans within the United States, many of whom lack up-to-date travel documents. Some previous legalization proposals contained a requirement that foreign nationals return home to obtain return visas (i.e., a "touch back" provision), and coordination and cooperation with Mexico could facilitate an orderly "touch back" process. On the other hand, the United States alone would determine who among millions of unauthorized aliens may be eligible for legalization. While Mexico would be a large stakeholder in any legalization program, such a program would not require an agreement with Mexico; and some may argue that a bilateral legalization program would not be in the national interest. Poverty and a lack of economic opportunities have been major drivers of Mexico-U.S. migration, and scholars have long suggested that fostering development in Mexico could reduce unauthorized migration flows. IRCA established a Commission for the Study of International Migration and Cooperative Economic Development charged with "consult[ing] with the governments of Mexico and other sending countries in the Western Hemisphere" and "examin[ing] the conditions in Mexico and such other sending countries which contribute to unauthorized migration to the United States." The commission concluded that economic development stimulates migration in the short term by raising expectations and providing people with the resources to emigrate, but that economic development and job creation are "the only way to diminish migratory pressures over time." As part of its poverty-alleviation efforts, Mexico has supported cash remittances from migrants in the United States to migrant communities of origin in Mexico. Such remittances exceed $20 billion annually, and have become a key source of income for many households. In particular, Mexico has helped migrants gain access to banks and other formal remittance channels rather than using informal money transfer systems, which are less reliable and which typically charge high fees to transfer funds. Since 2002, the Mexican government also has supported the "3 X 1 Citizen's Initiative." Under this program, remittances sent from Mexican home town associations (HTAs) in the United States are matched dollar for dollar by each level of the Mexican government (municipal, state, and federal). In 2005, Western Union began to contribute its own matching funds for a "4+1" matching program to support micro-enterprise initiatives funded by HTAs. The 3 X 1 program remains limited in scope, however, with a federal budget of about $38 million in 2010, compared to total remittance flows of about $22.6 billion that year. The United States provided about $178 million in foreign assistance to Mexico in FY2011, including about $25 million in development aid and $143 million under the Mérida Initiative. Should foreign assistance to Mexico be focused on creating alternatives to emigration? Some people have suggested that the United States should support development projects in Mexico to discourage unauthorized emigration. One suggestion is to have the U.S. Agency for International Development support farmer-to-farmer exchange programs to connect rural farmers' cooperatives in Mexico with Mexican farmers in the United States. Another possibility would be to expand the mandate of the North American Development Bank from environmental infrastructure projects to also include broader development goals. Yet as an upper middle-income developing country by World Bank standards, Mexico does not receive large amounts of U.S. development aid. Moreover, using economic assistance as a tool to reduce emigration may be challenging because even if economic development creates jobs and reduces emigration in the long run, development may be associated with increased migration flows in the short run as a result of rising expectations and market dislocations. The United States also supports Mexican counter-narcotics efforts through the Mérida Initiative. Given evidence that drug trafficking-related violence may contribute to unauthorized emigration, strengthening the social fabric in violence-prone communities could help reduce such flows. Whereas U.S. assistance under the Mérida Initiative initially focused on training and equipping Mexican counterdrug forces, it now targets the weak law enforcement institutions and underlying societal problems that have allowed the drug trade to flourish in Mexico. Pillar four of the "Beyond Mérida" framework aims to build strong and resilient communities that can withstand the pressures of crime and violence, thereby mitigating citizens' needs to emigrate for safety. Congress could consider migration dynamics in the design of such programs in the future. On the other hand, some people may object as a matter of principle to any effort to target U.S. funding to Mexican emigration communities. Some people also have proposed linking foreign assistance to illegal migration through another mechanism: by reducing foreign aid to Mexico in proportion to the number of illegal border crossers. History and geography guarantee that Mexico and the United States have a unique migration relationship—a point driven home by Mexico's ranking as the number one source of U.S. immigrants, both legal and unauthorized. The size of the Mexican population in the United States, its demographic characteristics, and its increasing dispersion to new U.S. destinations all place Mexico at the center of the U.S. immigration debate; and the proportion of Mexicans who migrate to the United States also places migration issues at the center of the bilateral relationship. As described above, these flows are a function of economic push and pull factors and of previous policy decisions. This history directs attention to policy choices being made today. Many of the core issues in the U.S. immigration debate—including efforts to strengthen migration control and border security, possible reforms to the lawful permanent resident and nonimmigrant visa systems, and proposals to legalize certain unauthorized migrants—have important implications for both countries. The United States and Mexico also may share common interests around some of these issues, such as combating smuggling and other transnational crime, encouraging circularity among temporary workers, promoting the orderly repatriation of unauthorized Mexicans and criminal aliens, and generally reducing unauthorized migration. Thus, as in the past, some people in the United States may see reasons to treat Mexico as a "special case" on certain immigration questions. From this perspective, previous Mexico-U.S. migration policies not only help explain the scope of contemporary flows, but also set a precedent for those who may favor taking a bilateral approach. These factors also get at the practical argument for Mexico-specific policies: the sheer size of the bilateral flow and Mexico's status as America's continental neighbor mean that bilateral policies may offer promising opportunities for more effective migration enforcement and more efficient management of flows. These potential advantages underlay the 2001 framework agreement between George W. Bush and Vicente Fox that would have included a Mexico-specific temporary worker program, collaborative border enforcement, legalization for certain unauthorized Mexicans in the United States, and new investments in Mexican communities of origin aimed at reducing illegal outflows. The United States and Mexico may continue to see opportunities to better manage migration flows and control unauthorized migration through collaborative approaches to these issues, as discussed above. On the other hand, a truly collaborative approach to bilateral migration issues along these lines would require a high level of mutual trust. Some people may question whether Mexico would be a reliable partner in a bilateral visa program, border enforcement, or port security—nor is it clear that Mexico would be willing to take on such a role in all of these cases. At a minimum, any major changes in the U.S.-Mexican migration relationship likely would require that the countries first achieve greater success in combating illicit drugs and reducing the violence associated with the drug trade. In the long run, the future of the U.S.-Mexican migration relationship depends in great part on economic and demographic trends in both countries, and their impact on regional migration flows. What will be the shape of the U.S. economic recovery, and will U.S. employers continue to demand high levels of low-skilled migration? Will emigration from Mexico pick back up with the U.S. economic recovery, perhaps including more higher-skilled migrants, or have economic and demographic changes in both countries ushered in a new period of lower regional flows? As in the past, it will be a combination of these structural factors and of policy decisions in both countries that influences Mexico-U.S. migration flows. Appendix A. Total and Mexico-Born Population, by State, 1990, 2000, and 2010 Appendix B. Immigrant Visas, FY2000–FY2009 Appendix C. Nonimmigrant Visas Issued, Selected Types, FY2000-FY2009

Summary: History and geography have given Mexico a unique status in the U.S. immigration system, and have made the Mexico-U.S. migration flow the largest in the world. Mexicans are the largest group of U.S. migrants across most types of immigration statuses—a fact that may have important implications for how Congress makes U.S. immigration policy. This report reviews the history of immigration policy and migration flows between the countries and the demographics of Mexicans within the United States. It also analyzes contemporary issues in U.S. immigration policy and the impact Mexico may have on U.S. immigration outcomes. The U.S.-Mexican migration system has passed through four main phases since the early 20th century. Migration flows were limited and mainly short-term prior to the 1920s, and Mexicans were exempted from certain immigration restrictions and admitted as the first U.S. guest workers during World War I. The bilateral "Bracero" temporary worker program marked a second phase, with 4.6 million temporary visas issued to Mexican workers between 1942 and 1964. With the end of the Bracero program and other immigration reforms in 1965, along with social and economic changes in the United States and Mexico, the third stage was marked by growing illegal inflows, eventually leading Congress to pass the Immigration Reform and Control Act of 1986. Finally, despite a series of additional enforcement measures, the Mexican population in the United States doubled during each decade since 1970, with unauthorized migrants accounting for a majority of the growth, followed by legal family-based immigration. Today, the Mexico-born population in the United States stands at about 11.7 million people. Compared to other migrants, the Mexican born in the United States are more likely to be unauthorized, be younger, have lower education levels, work in lower-skilled occupations, and have lower measures of economic well-being. In contrast with earlier periods and virtually all other migrants, Mexicans are now dispersed throughout all 50 U.S. states. Given the size of the Mexico-born population in the United States and the 2,000-mile border shared between the two countries, Mexicans and Mexico are uniquely affected by U.S. immigration policies. Mexicans are the largest group of aliens subject to U.S. immigration control and border security policies, the largest group of lawful immigrants within permanent and temporary visa categories, and the majority of unauthorized migrants within the United States. On one hand, Mexico's prominence in the U.S. migration system means that U.S. immigration policy, to varying degrees, primarily affects Mexicans and Mexico. Today's Mexico-U.S. migration flows and the Mexico-born population in the United States are the product of previous immigration policy decisions, as well as of the long and complex history of the U.S. and Mexican economies, labor markets, and demographics. On the other hand, Mexico also remains at the center of today's immigration debate, though often only implicitly. Recognizing Mexico's status within the U.S. migration system focuses attention on how the U.S. immigration debate affects Mexico, and on how Mexico may affect certain migration outcomes. Mexico's role in the U.S. immigration system, along with the importance of the bilateral relationship to both countries, creates a number of opportunities, and challenges, as Congress weighs changes to U.S. immigration policy. First, Mexico already plays a key role in U.S. immigration enforcement and border security. The United States and Mexico share information about transnational threats, Mexico combats illegal migration by third country nationals, and Mexico supports certain U.S. enforcement efforts related to the repatriation of Mexican nationals. This report explores possibilities for additional bilateralism in these areas, including strategies to reduce recidivism among illegal migrants and to better manage U.S.-Mexican ports of entry. Second, with respect to lawful permanent immigration, Mexico benefits from rules that favor family-based flows, but still dominates the waiting lists of people with approved immigration petitions for whom visas have not yet been made available. The analysis here focuses attention on recent proposals to reduce visa backlogs and on other reforms that could affect the number of immigrant visas for Mexico. Third, Mexico dominates temporary visa categories for low-skilled workers, and an increasing number of Mexicans could also qualify for high-skilled worker visas. The report reviews previous experience with Mexico-specific temporary worker programs, which offer mixed lessons about managing flows this way. Additional policy considerations concern potential legalization proposals and efforts to reduce unauthorized emigration from Mexico. Given the large number of unauthorized Mexican migrants in the United States, Mexico could play a role in a potential legalization program, including by providing information to verify migrants' identities and by facilitating proposed "touch-back" requirements. Finally, in the long run, economic development and employment creation in Mexico are widely viewed as being among the best tools to reduce unauthorized emigration. While demographic and economic trends in Mexico likely have already contributed to reduced illegal outflows, the relationship between international trade and financial flows, U.S. economic assistance, and economic opportunities in Mexico may represent promising areas for policies to reduce illegal migration in the future. This report supplements other CRS research on Mexico (such as CRS Report RL32724, Mexico: Issues for Congress; and CRS Report R41349, U.S.-Mexican Security Cooperation: The Mérida Initiative and Beyond ) and on immigration (such as CRS Report R42036, Immigration Legislation and Issues in the 112th Congress; and CRS Report R42138, Border Security: Immigration Enforcement Between Ports of Entry).