U.S. Demographic Projections

We have considered the United States’ demographic past. What of America’s demographic future?

In the short term, continued growth is a near certainty. Currently, the U.S. population is growing at around 3 million people per year. Long-term, a number of potential and divergent demographic paths open out. Which one the United States follows will depend on the four main factors that determine change in any population: fertility, mortality, immigration, and emigration.

In the first half of this report, we review several recent U.S. population projections, mostly out to 2050 or 2060. In the second half, we provide new population projections out to 2100. It is these projections to 2100 that will provide the basis for the alternatives analyzed in the full EIS on U.S. immigration policy.

While demographers use a number of different methods to project potential population changes, the most popular, particularly for long-term forecasting, is the “cohort-component” method. Essentially, we start with a certain population with a particular age-structure. Then we take that population forward in time as it responds to four key factors: births (fertility), deaths (mortality), immigration, and emigration. These last two factors are sometimes combined as “migration” or “net migration.” Brian O’Neill and colleagues summarize the method, in an introductory discussion, as follows:

Initial populations for countries or regions are grouped into cohorts defined by age and sex, and the projection proceeds by updating the population of each age- and sex-specific group according to assumptions about three components of population change: fertility, mortality, and migration. Each cohort survives forward to the next age group according to assumed age-specific mortality rates. Five-year age groups (and five year time steps) are commonly used (although not strictly necessary) for long-range projections.

As an example, the number of females in a particular population aged 20-25 in 2005 is calculated as the number of females aged 15-20 in 2000 multiplied by the assumed probability of survival for females of that age over the time period 2000-2005. This calculation is made for each age group and for both sexes, and repeated for each time step as the projection proceeds.

Migration can be accounted for by applying age- and sex-specific net migration rates to each cohort as well, and ensuring that immigration equals emigration when summed over all regions.

The size of the youngest age group is also affected by the number of births, which is calculated by applying assumed age-specific fertility rates to female cohorts in the reproductive age span. An assumed sex ratio at birth is used to divide total births into males and females.[1]

All the recent population projections discussed in this document use the cohort-component method. So do we in our own population projections. For more on basic demographic projection techniques and the cohort-component method, see O’Neill et al., A Guide to Global Population Projections.[2]

Recent Population Projections

In 2000, the U.S. Census Bureau provided population projections out to 2100. This was a rare instance of the Bureau developing 100-year projections. The Census Bureau developed four main “series,” built in the standard way around different fertility, mortality, immigration, and emigration scenarios.[3] The middle series incorporated what the Bureau believed to be the most likely scenarios regarding each of these factors. The lowest and highest series incorporated the lowest and highest plausible scenarios for each of these factors. Finally, the zero net international migration series combined the most likely fertility and mortality scenarios (according to the Bureau) with zero net migration (immigration exactly balanced by emigration). This procedure led to the following projections[4]:

  Lowest Middle Highest Zero Net immigration
2000 274,853 275,306 275,816 273,818
2010 291,413 299,862 310,910 287,710
2020 303,664 324,927 354,642 301,636
2030 311,656 351,070 409,604 313,219
2040 314,673 377,350 475,949 321,167
2050 313,546 403,687 552,757 327,641
2060 310,533 432,011 642,752 334,724
2070 306,589 463,639 749,257 343,815
2080 300,747 497,830 873,794 354,471
2090 292,584 533,605 1,017,344 365,689
2100 282,706 570,954 1,182,390 377,444

Because the three main series varied fertility, mortality and immigration simultaneously, they are of little value in distinguishing the relative contributions of each of these factors to population growth. However, the large variation between the lowest and highest series (a difference of 899 million people by 2100) does vividly convey the power of these demographic factors to shape the future in very different ways, relatively quickly (in this case, over a mere 100 years).

In addition, considering the zero net migration series shows that even without any net in-migration, the U.S. population is set to grow considerably over the coming century: by 103 million people, according to this projection. Meanwhile, comparison of the middle or “most likely” series with the zero net migration series demonstrates that immigration is ready to make an immense contribution to population growth, with the difference between the most likely series and zero immigration standing at 194 million people over the course of the 21st century.

*

In 2008, the Census Bureau projected U.S. population numbers out to 2050, primarily by extrapolating out then-current trends regarding fertility rates, mortality rates, and immigration rates. Based in part on recent National Center for Health Statistics data on deaths and births, Bureau demographers predicted a 4-year to 5-year increase in the average American lifespan and nearly static average fertility rates during this period (with decreases in native fertility offset by greater numbers of immigrants, who tend to have higher fertility rates). They also predicted a steady rise in net international immigration, from 1.2 million in 2001 to over 2 million in 2050.[5]

Based on these predicted trends, Census Bureau demographers came up with a medium (or “most likely”) projection of 439 million people in 2050. This would represent a 158 million-person (56%) increase over 2000.[6]

*

The following year, the Census Bureau delivered a further series of projections. These followed the same basic parameters as the 2008 projections. But this time, the Bureau held fertility rates and longevity constant among the different projections, while varying immigration levels between zero and two million annually.[7] The 2009 projections came out as follows:

Average annual net immigration Population in 2050
zero 323 million
1 million 399 million
1.5 million 423 million
2 million 458 million

The 2009 Census Bureau projections demonstrate that the actual immigration rates that occur will make an immense difference to future U.S. population numbers. The difference between zero net immigration (in 2009) and the Bureau’s most likely scenario (in 2008) was 116 million people (a number equal to the total U.S. population in 1925). The difference between zero net migration and two million annual net migration in the 2009 projections was 135 million people. According to these projections, each additional million annual immigrants post-2009 added, on average, 67.5 million people to the United States population in 2050.

*

Other studies have confirmed the impact immigration is likely to have on America’s future population. A study published by the Pew Research Center in 2008, “U.S. Population Projections: 2005–2050,” reached the following conclusions:

• Between 2005 and 2050, the nation’s population will increase to 438 million from 296 million, a rise of 142 million people that represents growth of 48%.

• Immigrants who arrive after 2005, and their U.S.-born descendants, account for 82% of the projected national population increase during the 2005–2050 period.

• Of the 117 million additional people attributable to the effect of new immigration, 67 million will be the immigrants themselves and 50 million will be their U.S.-born children and grandchildren.[8]

In addition to their “main” or most likely projection, in which immigration averaged 1.7 million annually, the Pew researchers ran “lower immigration” and “higher immigration” projections, in order to see how future population numbers would change under different immigration scenarios. The lower immigration projection averaged 900,000 immigrants annually (50% lower than predicted) and the higher immigration scenario averaged 2.6 million annually (50% higher than predicted). These led to the following projected populations in 2050:

Average annual net immigration Population in 2050
900,000 384 million
1.7 million 438 million
2.6 million 496 million

Once again, we see that changes in immigration levels make a large difference to future population numbers. The difference between a 50% decrease and a 50% increase in immigration, both well within the realm of policy options discussed in the U.S. Congress during the past decade, was 112 million people more or less in 2050.[9]

*

In December 2012, researchers at Decision Demographics, Inc., in consultation with the Center for Immigration Studies, recreated the U.S. Census Bureau’s 2008 population projections, using data provided by the Census Bureau.[10] Using the resulting projection tool, researchers at D.D. and C.I.S. then varied the level of net migration to create a new series of projections, in order to better discern immigration’s potential impact on the U.S. population. In summarizing their findings, Steven Camarota concluded that: “If immigration continues as the Census Bureau expects, the nation’s population will increase from 309 million in 2010 to 436 million in 2050 — a 127 million (41 percent) increase.” He added: “The projected increase of 127 million is larger than the combined populations of Great Britain and France. It also exceeds the entire U.S. population in 1930.”[11] Conversely, reducing immigration could significantly reduce population growth over this period (but could not eliminate it entirely), as shown in the figure below:

Impact of Immigration on U.S. Population Size, 2010-2050 (millions)

While the 2008 Census Bureau projections only went out to 2050, it is possible to use the projection tool created by Decision Demographics and C.I.S. to generate projections out to 2100. To do so, researchers assumed that the levels of immigration, fertility, and mortality in 2050 foreseen by the Census Bureau continued to 2100. Then once again, they varied immigration levels, this time both above and below the Census Bureau projections, in order to isolate immigration’s potential contribution to population growth. This generated the projections shown in the figure below:

Impact of Immigration on U.S. Population Size, 2010-2100 (millions)
 

As Camarota summarizes their findings: “If the level of immigration the Census Bureau foresees in 2050 were to continue after that date, then the U.S. population would hit 506 million by 2070 and slightly more than 617 million by 2100. This means that the U.S. population would double during this century from slightly more than 309 million in 2010 to more than 600 million by 2100.” While according to these projections a zero net immigration regime would stabilize the U.S. population at approximately our current numbers, immigration at even one-fourth the rate projected by the Census Bureau in 2008 would lead to a population 85 million larger in 2100 (and poised to continue growing). Camarota concludes: “It would take a very substantial reduction in immigration to stabilize the size of the U.S. population by 2100. In fact, immigration at almost any level will cause the country to be a good deal larger by 2100 than it would be in the absence of immigration.”[12]

*

Also in December 2012, the U.S. Census Bureau released new “50-year” (actually 48-year) population projections out to 2060. According to the Census Bureau: “The [U.S.] population is projected to increase from 314 million in 2012 to 420 million in 2060.”[13] This would represent a 34% increase, or 106 million more people living in the U.S. in 2060 than in 2012.

The new projections forecast significantly slower population growth than was predicted in the 2008 Census Bureau projections. According to the Census Bureau, “most of the difference is explained by decreases in the level of net international migration in the 2012 series compared to the 2008 series.”[14] For example, the 2008 projections forecast net immigration of 1.377 million in 2015, while the 2012 projections forecast 794,000 net immigration: a difference of 583,000. This difference grows over time: by 2050, the 2008 projections forecast 2.047 million net immigration, while the 2012 projections forecast 1.204 million net immigration: a difference of 843,000.[15]

The Census Bureau’s new projections appear to have been significantly influenced by the large decrease in illegal immigration into the U.S. in the wake of the 2007 recession. Whether lower levels of illegal and (more importantly) total immigration will continue in better economic times is a matter for debate; current proposals being considered by Congress could greatly increase annual immigration levels. What seems clear, once again, is that apparently small changes in annual immigration levels can lead to large changes in overall population numbers, in a relatively short time. Lowering projected immigration between 2012 and 2050 decreased the estimated U.S. population in 2050 by 39 million people (400 million in the 2012 projections, as compared to 439 million in the 2008 projections).[16]

Population Projections Used In This Study

In preparing the population projections used in this study, we have employed the demographic projection tool developed by Decision Demographics and the Center for Immigration Studies, which they have kindly shared with us. As noted above, these researchers replicated the model created by the Census Bureau for its 2008 and 2009 population projections.[17] The resultant projection tool allows users to vary fertility levels and immigration levels; hence, it can take into account the Bureau’s revised 2012 projections. Crucially, it also allows users to run projections out to 2100. Because discussions of immigration policy are routinely hampered by short-term thinking, we wanted this EIS to take a more long-term view. Hence the decision to run (near) 100-year projections, rather than the more common 50-year projections.

Use of the D.D./C.I.S. projection tool allows us to ground our projections in the best available demographic data, and the most plausible fertility and mortality assumptions for the coming 90 years, while considering how different immigration policies could change total U.S. population numbers over the course of this period. As already noted, these projections are derived using the cohort-component method, the standard method used by demographers for national population projections.[18]

*

In creating our population projections, we held fertility and morality rates steady under all scenarios, at the levels predicted by the Census Bureau in its 2008 projections. The rationales for these particular fertility and mortality rates may be found in the methodology statement for the Census Bureau’s 2008 projections, which should be compared with the methodology statement prepared for the Bureau’s 2012 projections.[19] Then we varied annual immigration levels in half million annual increments, phasing in any changes from current immigration levels over six years, starting in 2014 and ending in 2020. This generated the following 90-year population projections:

Population Projections to 2100 Under Different Immigration Levels

Average annual net immigration Population in 2010 Population in 2050 Population in 2100
zero 309 million 358 million 343 million
500,000 309 million 380 milllion 415 million
1 million 309 million 403 million 486 million
1.5 million 309 million 426 million 560 million
2 million 309 million 449 million 629 million

At zero annual net immigration (immigration set equal to emigration), America’s population continues to increase for about forty years, and then slowly decreases to 343 million total, for an overall increase of 34 million people over 2010. Under this scenario, the U.S. could begin to stabilize or slowly reduce our population from current levels.

If Congress followed the recommendations made by the Jordan Commission on Immigration Reform in the mid-1990s,[20] cutting immigration to approximately 500,000 net annually, the U.S. population would still grow significantly according to our projections: to 415 million by 2100. That would represent an increase of 106 million people over 2010. Population stabilization would be in sight by then, albeit at a much higher level, provided future political leaders were willing to cut immigration even further or U.S. fertility decreased significantly.

In a third scenario, readers may imagine Congress holding legal immigration steady at approximately its current level, one million net annually, while succeeding Presidential administrations rein in illegal immigration. Under this scenario (which still represents a significant decrease from current immigration levels), America’s population would increase by 177 million to 486 million total. Perhaps just as important, in 2100 the U.S. would be set to continue on an upward demographic trajectory, with no population stabilization in sight.

In a fourth scenario, we set total immigration near the recent heights seen in the first few years of the 21st century, at 1.5 million net immigration annually. Under this scenario, the U.S. population would reach 560 million by 2100. The population would increase by 251 million people and the growth curve would angle even more steeply upward.

In our final scenario, we imagined immigration increasing to 2 million net annually. This is roughly the level currently being considered under several “comprehensive immigration reform” bills being debated in Congress. Under this scenario, the U.S. population would approximately double, to 629 million people. In addition, the population in 2100 would be set to increase by tens of millions more for many years to come, as in the previous two scenarios.

These five population projections may be graphed as follows:

US Population Projections to 2100 under Five Different Scenarios
 

As the chart above illustrates (and as we saw in the previous section’s summary of recent population projections by the Census Bureau and independent demographers), immigration makes a big difference to future U.S. population numbers. A good rule of thumb is that for every extra half million immigrants admitted annually, America’s population in 2100 is increased by about 72 million people. Another is that under all mass immigration scenarios, with more than a few hundred thousand net immigrants per year, the U.S. population cannot stabilize and instead continues to grow.

It remains true that major changes to any of the four key demographic factors could significantly change the trajectory of U.S. population growth in the 21st century. If death rates increase, that will slow growth, as AIDS has slowed population growth in some countries in sub-Saharan Africa. Conversely, medical advances that extend life spans could cause the U.S. population to grow even more quickly. Similarly, a mass exodus of American citizens (increased emigration) or a widespread trend to refrain from childbearing (decreased fertility rates) could slow growth, and in extreme scenarios even lead to population decreases, despite continued mass immigration.

Still, in the short to mid-term, all such possibilities seem unlikely and, except perhaps for some reduction in native fertility, unwelcome. They also seem relatively impervious to policy interventions: we are not likely to offer incentives for citizens to emigrate (although some overpopulated countries do provide such incentives) or to have fewer children. Such slight incentives for the latter as might be legislated are unlikely to bend the U.S. demographic curve significantly. In contrast, immigration policy can be changed quickly and radically via Congressional legislation, as was shown in 1924 and 1965. So for the foreseeable future, immigration policy seems likely to remain the primary means to regulate U.S. population growth.

A Demographic Note on the Need to Take Longer Views

Immigration’s impact on the overall U.S. population becomes clearer when we take longer views. This is both because population growth tends to accumulate and because, in the case of the United States (and several other developed nations with relatively high immigration levels), mass immigration prevents us from ever taking advantage of our replacement-level fertility rate and stabilizing our population. This point becomes clear when we compare 40-year, 90-year and 190-year population projections under the five immigration scenarios previously analyzed (zero, 500,000, 1 million, 1.5 million and 2 million annual net migration).

The forty-year population projections do suggest the different population trajectories entrained by these different immigration scenarios. However the United States’ current population momentum, built in to every scenario, combined with the short duration considered, tends to obscure the magnitude of the differences to which each path commits us. Populations differ in 2050 by an average of 23 million people:

U.S. Population Projections to 2050 under Five Different Scenarios
 

The ninety-year population projections, by contrast, allow us to see how different immigration scenarios will impact the U.S. population a full three generations into the future. Populations differ in 2100 by an average of 71.5 million people. The difference in the trajectories regarding future population growth is also much clearer in these projections:

U.S. Population Projections to 2100 under Five Different Scenarios

Finally, 190-year projections were made by piggybacking onto the 90-year projections: taking the average decadal percentage of population change from 2090 to 2100, under each scenario, and projecting out that percentage of population change for an additional ten decades. Decadal (not annual) rates of population change under the five different scenarios ran as follows:

Average annual net migration Percentage population change between 2090-2100
zero -- 1.3%
500,000 + 1.4%
1 million + 3.4%
1.5 million + 4.9%
2 million + 6.1%

Although these projections to 2200 are highly speculative, they do allow us to consider the potential demographic impacts of immigration policy a full “seven generations” into the future. After all, the United States has existed as a nation for more than 190 years, and most Americans  probably hope their country continues to thrive sustainably for another 190 years and even longer.

U.S. Population Projections to 2200 under Five Scenarios
 

The high projection of 1.168 billion is roughly equal to the current populations of China and India. Comparing the two lower-immigration scenarios in the chart above suggests two interesting points. First, that the U.S. might be able to maintain a robust (~300 million) population in the absence of any net immigration, at least for the foreseeable future. Second, that immigration beyond a few hundred thousand people annually might make stabilizing the U.S. population impossible, at least without substantial decreases in American fertility rates. [21]

Comparing the three higher-immigration scenarios suggests that current immigration policies are likely committing the U.S. to a much larger total population in the future. They also imply that some of the reforms to immigration policy currently being proposed could swell that population by hundreds of millions more people within “seven generations.” Under these long-term population projections, each additional 500,000 annual immigrants add an average of 217 million people to the U.S. population in 2200.

We summarize the short-term, medium-term and long-term population projections under our five scenarios below:

Average annual net immigration Population in 2010 Population in 2050 Population in 2100 Population in 2200
zero 309 million 358 million 343 million 299 million
500,000 309 million 380 million 415 million 479 million
1 million 309 million 403 million 486 million 688 million
1.5 million 309 million 426 million 560 million 919 million
2 million 309 million 449 million 629 million 1.168 billion

The short-term (40-year) population projections would be easiest to defend in a room full of demographers, as plausible estimates for what might actually occur over the next forty years. The best rationale for considering the long-term (190-year) population projections is that they vividly convey the demographic implications of the path we are on and of alternative paths that Americans might consciously pursue. For purposes of this EIS, we opt for a middle course and choose to use the mid-term (90-year) population projections for detailed analysis. These projections are defensible in terms of the plausibility of the parameters chosen (fertility rates, mortality rates, net migration rates) and the projection methodology. Yet they arguably allow us to peer far enough into the future to act responsibly.

In ninety years, we expect that most children born to children alive today will still be alive themselves. And we earnestly hope that our descendants will be living good lives. Perhaps, then, this is the shortest time frame within which we can consider the implications of today’s major population and environmental policies, while still legitimately claiming to seriously consider the ecological sustainability of those policies. In the work to come on this environmental impact study on U.S. immigration policy, that is what we propose to do.



[1] Brian C. O'Neill, Deborah Balk, Melanie Brickman and Markos Ezra. 2001. “A Guide to Global Population Projections.” Demographic Research volume 4, article 8, pages 203-288.

[2] For a more detailed introduction to basic demography, see David Yaukey, Douglas Anderton and Jennifer Lundquist, Demography: The Study of Human Population, 3rd edition (Prospect Heights, IL: Waveland Press, 2007), or Dudley Poston, Jr. and Leon Bouvier, Population and Society: An Introduction to Demography (Cambridge: Cambridge University Press, 2010).

[3] Frederick Hollmann, Tammany Mulder and Jeffrey Kallan, “Methodology and Assumptions for the Population Projections of the United States: 1999 to 2100.” Population Projections Branch, Population Division, Bureau of the Census, Washington, DC. January, 2000 (Population Division Working Paper No. 38).

[4] U.S. Census Bureau, "Annual Projections of the Total Resident Population as of July 1: Middle, Lowest, Highest, and Zero International Migration Series, 1999 to 2100. Washington, D.C.: U.S. Census Bureau, 2000.

[6] U.S. Census Bureau, “2008 National Population Projections,” Table 1. Projections of the Population and Components of Change for the United States: 2010 to 2050”.

[7] J.M. Ortman and C.E. Guarneri, “United States Population Projections: 2000 to 2050” (Washington, DC: Census Bureau, 2009).

[8] Jeffrey Passel and D’Vera Cohn, U.S. Population Projections: 2005-2050 (Washington, DC: Pew Research Center, 2008), pp. 8-9.

[9] Ibid., p.23.

[10] Stephen Tordella, Steven Camarota, Tom Godfrey and Nancy Rosene, “Evaluating the Role of Immigration in U.S. Population Projections” (Washington, DC: Center for Immigration Studies, 2012) (unpublished essay).

[11] Steven Camarota, “Projecting Immigration’s Impact on the Size and Age Structure of the 21st Century American Population” (Washington, DC: Center for Immigration Studies, December 2012).

[12] Ibid., p.16.

[13] U.S. Census Bureau, “Methodology and Assumptions for the 2012 National Projections” (Washington, DC: December 2012), p.11.

[14] Ibid.

[15] Ibid., table 8, page 31.

[16] Ibid., tables 5 and 8, pp. 28, 31.

[17] Stephen Tordella et al., “Evaluating the Role of Immigration in U.S. Population Projections”; Steven Camarota, “Projecting Immigration’s Impact on the Size and Age Structure of the 21st Century American Population.”

[18] See O'Neill et al., “A Guide to Global Population Projections,” or any introductory textbook in demography.

[19] See U.S. Census Bureau, “2008 National Population Projections: Methodology and Assumptions”, and U.S. Census Bureau, “Methodology and Assumptions for the 2012 National Projections” (Washington, DC: December 2012), p.11.

[20] U.S. Commission on Immigration Reform, Becoming an American: Immigration and Immigrant Policy (Washington, DC: US Government Printing Office, 1997).

[21] This second point is discussed in Camarota, “Projecting Immigration’s Impact on the Size and Age Structure of the 21st Century American Population.”