Fifty years from now the US will have 20 million fewer residents than previously forecast, according to the Census Bureau’s new national population projections released last week, which will translate in reduced demand for housing than expected

The bureau’s new projected population of 420.3 million in 2060 is below its previous projection of 439 million for a decade earlier, in 2050. The bureau’s new projected population for 2050 is 399.8 million. The 2060 population figure, which represents a 34 percent increase from the U.S. 2012 population of 314 million, assumes that annual growth will range from just below 2 million to 2.5 million rather than about 3 million to 3.4 million people each year, as previously assumed. The new estimates lowers the Census forecast by 4 percent.

Most of the 39.2 million gap in the total population forecast is due to scaled-back assumptions about the level of new immigration to the U.S. But another notable factor in the lowered population projection was that the bureau also lowered its forecasts for birth levels. Immigration levels have come down since a peak in 2001, and unauthorized immigration began falling around 2007. Birth rates, already decreasing in recent decades, declined sharply after 2007. The Great Recession that began in 2007 has helped to slow immigration and births

In its new projections, the bureau assumes that the U.S. population will gain a total of 41.2 million net new international migrants from 2012-2050. In its 2008 projections through 2050, that number was 65.6 million. As this chart shows, the difference-24.4 million-represents more than 60 percent of the reduction in total U.S. population size for 2050 in the 2012 projections compared with those in 2008.

Not only did the bureau lower the number of new immigrants it expects to arrive, it also changed the way it calculates its immigration forecasts. Instead of using only U.S. data, the bureau incorporated information on population trends in sending countries, which it collects in its International Data Base.

Overall, the projections estimate that net immigration levels will rise to 1.2 million a year in 2060 from 725,000 in 2012. In the new projections, the growth of the foreign-born population increases less and less rapidly over time and virtually levels off by mid-century. In the 2008 projections, annual net immigration was about 1.3 million in 2012 and increased to 2 million in 2048, growing briskly each decade. (Net immigration from abroad includes a small number of people born in the U.S. or its territories, but not enough to affect totals.)