Office of Immigration Statistics

POLICY DIRECTORATE

Fact Sheet

NOVEMBER 2006

Naturalization Rate Estimates:

Stock vs. Flow

DEREKH D. F. CORNWELL

A commonly asked question about naturalization is whether immigrants from certain countries are

more likely to become U.S. citizens than immigrants from other countries.Two primary data sources

commonly used to calculate naturalization rates are the U.S. Census Bureau’s decennial census and

surveys,and the administrative records oftheDepartment ofHomeland Security (DHS).Naturalization

rates computed from these two data sources, however, may be quite different. This Office of

Immigration Statistics Fact Sheet explains why this happens and provides illustrative examples.

BACKGROUND

To understand why naturalization rates calculated from 

DHS and Census data differ, it is first important to 

understand the difference between a stock and a flow 

(see Box 1).

Census data provide a cross sectional snapshot of the 

foreign-born population or “stock” living in the United 

States at a given point in time by citizenship status 

and year of entry. These data measure the proportion 

of the foreign born population at a point in time that 

is naturalized. However, this does not provide an 

indication of the frequency with which immigrants are 

naturalizing. The numerator – namely, the naturalized 

citizen population – consists of the survivors of sameyear entry cohorts of immigrants reduced by mortality 

and emigration. The denominator – namely, the total 

foreign-born population – includes many noncitizens,

such as temporary workers, foreign students, and 

undocumented immigrants, who are not eligible to 

naturalize as of the survey date. Thus, the denominator 

does not exclusively capture the subset of the foreignborn population that is at risk to naturalize.

Since 1973, DHS has maintained data electronically from 

the applications of immigrants who are granted LPR status 

and naturalize. These data essentially capture the “flow”

of LPRs and persons naturalizing. By matching LPR and 

naturalization records for the same individuals, naturalization rates may be calculated for persons who obtained 

LPR status at the same time (e.g. same-year). The DHS 

naturalization rates measure the number of immigrants 

who have naturalized as a proportion of all those who 

obtained LPR status at the same time and are thus eligible 

to naturalize. In this respect, rates calculated from DHS 

data more accurately reflect the propensity of LPRs to 

naturalize than do the rates obtained from Census data 

(proportion naturalized). The DHS rates, however, are 

based on data from 1973 through 2004. Naturalization 

tends to be concentrated in the first few decades of 

eligibility although there is no age limit.While DHS rates 

calculated for LPRs in the 1970s cohorts are relatively 

complete, the rates for the 1990s cohorts are relatively

incomplete and do not provide an accurate representation

of lifetime likelihood of naturalization. In addition, DHS

naturalization rates are based on all LPRs and do not include

adjustments for subsequent emigration or mortality.

Box 1. 

Definitions of Stock vs. Flow

Stock: The population at a point in time. Example: the 

number of naturalized citizens residing in the United 

States on January 1, 2004.

Flow: Additions (or subtractions) to the existing stock 

during a specified period of time. Example: the number 

of persons who naturalized during each year 1975 

through 2004.

METHOD

Naturalization rates calculated from DHS and Census 

data were compared for two cohorts: 1975 and 1995.

The 2004 American Community Survey (ACS) was the 

source for Census data. For the ACS, the cohorts were 

approximated by year of entry. This approximation is 
2 DHS Office of Immigration Statistics

Table 1: 

DHS and ACS Naturalization “Rates” of Immigrants Ages 16 and Over from Ten Largest Source Countries

Country of origin

Department of Homeland Security American Community Survey

Year of LPR status Year of entry

1975 1995 1975 1995

Total 

LPR flow

Percent 

naturalized 

through 2004

Total LPR 

flow

Percent 

naturalized 

through 2004

Total foreignborn population

Percent 

citizen 

in 2004

Total foreignborn population

Percent 

citizen 

in 2004

 Total 1 . . . . . . . . . . . . . . . 283,010 58 572,672 46 491,053 76 987,311 28

Mexico . . . . . . . . . . . . . . . . . 41,045 47 71,800 18 127,598 54 314,682 11

Philippines. . . . . . . . . . . . . . . 25,080 71 40,022 51 27,661 86 41,222 45

Vietnam. . . . . . . . . . . . . . . . . 1,760 78 34,660 68 101,387 92 39,861 56

El Salvador . . . . . . . . . . . . . . 1,680 70 10,185 27 10,909 68 30,433 12

China . . . . . . . . . . . . . . . . . . 14,375 72 26,496 53 13,714 98 41,708 38

India . . . . . . . . . . . . . . . . . . . 13,670 71 30,869 58 17,973 95 43,788 32

Korea . . . . . . . . . . . . . . . . . . 17,085 71 12,200 39 14,027 86 10,948 25

Dominican Republic . . . . . . . . 9,247 53 22,583 18 4,767 90 24,987 23

Jamaica. . . . . . . . . . . . . . . . . 6,039 61 12,148 42 9,642 90 18,442 45

Haiti . . . . . . . . . . . . . . . . . . . 3,845 64 10,773 37 6,495 84 12,553 40

1 Total includes all sending countries.

Note: Ten largest source countries are ranked based on each country’s contribution to the total foreign-born population residing in the United States according to the 2004 American Community Survey.

Source: U.S. Department of Homeland Security and U.S. Census Bureau.

necessary because the ACS does not ask non-citizens about their 

legal status, which means the date LPR status was granted cannot 

be determined. For DHS data, the two cohorts were represented 

by persons who obtained LPR status in either 1975 or 1995 and 

who may have naturalized through 2004. Both the ACS and DHS 

data were restricted to persons ages 16 and over because the lower 

bound for DHS naturalization data is 18 years.

FINDINGS

The results reported in Table 1 demonstrate that estimates of 

cohort naturalization rates can vary widely depending on the data 

source used to estimate them. According to the ACS, for example,

the “rate” of naturalization for the 1975 year of entry cohort was 

76 percent as of 2004. By contrast, the DHS rate of naturalization 

for the 1975 LPR cohort was only 58 percent through fiscal year 

2004. On the other hand, while the ACS reports a naturalization 

rate of 28 percent through 2004 for the 1995 cohort, the DHS rate 

for the 1995 LPR cohort is 46 percent. Relying on ACS data to calculate the naturalization rates can give estimates quite wide of the 

mark compared with estimates obtained from DHS data.

The naturalization rates calculated from the two data sources also 

differ by country of origin. For the 1975 cohort, the ACS indicates that, of the ten largest sending countries listed in Table 1, the 

three with the highest naturalization rates as of 2004 were China 

(98 percent), India (95 percent), and Vietnam (92 percent).

The countries with the lowest naturalization rates were Mexico 

(54 percent), El Salvador (68 percent), and Haiti (84 percent).With 

the sole exception of Mexico, which retained the lowest naturalization rate across data sources, these rankings change when DHS 

data are used. For the 1975 LPR cohort, the sending countries with 

the highest naturalization rates are Vietnam (78 percent), China 

(72 percent),and the Philippines,India,and Korea (all at 71 percent).

Naturalization rates were lowest for LPRs from Mexico (47 percent) 

and the Dominican Republic (53 percent).This general pattern also 

holds for the more recent 1995 cohort. For this cohort, immigrants 

from Vietnam had the highest rate of naturalization through 2004 

according to the ACS and DHS (56 and 68 percent, respectively). A 

similar result holds for the lowest end of the distribution as well,

as the 1995 Mexican cohort again had the lowest rate of naturalization according to both data sources.

The potential for large disparities in naturalization rates is also 

demonstrated by examining the 1995 Haitian cohort in particular. As noted above, the ACS estimates suggest that Haitians who 

entered the United States in 1995 were in the upper half of the top 

ten source countries with respect to naturalization, which would 

make them among the most likely groups among the top sending 

countries to have naturalized as of 2004.The DHS estimates, on the 

other hand, suggest that the 1995 Haitian LPR cohort was in the 

bottom half of the ten-country naturalization distribution.Accordingly, the results indicate that, relative to the same cohort from the 

top ten sending countries, this group was actually among the least

likely to naturalize through 2004. Again, this result underscores 

the idea that estimating and comparing naturalization rates based 

on ACS and DHS data will yield different results.

CONCLUSION

This analysis illustrated the differences that result when calculating 

and comparing naturalization rates for immigrants from different 

countries using ACS and DHS data. Because the rate of naturalization 

is conceptually more similar to a measure of flow than stock, and 

eligibility to naturalize is restricted to a certain subset of immigrants 

(LPRs), data sources that capture both these characteristics will 

produce more accurate naturalization estimates than data sources 

that do not. Consequently, DHS data, which covers the population 

at risk to naturalize as well as the naturalization flow over time, are 

better suited than aggregate cross-sectional data sources, such as 

the ACS, to gauge immigrants’ propensity to naturalize.