The United States population this year showed the slowest growth since the Great Depression, and would have been even slower had it not been for an increase in immigrants, according to the 2016 U.S. Census Bureau report.

Nationally, the U.S. population grew only by 0.7% to 323.1 million. As baby boomers have continued to decline, they haven't been replaced by new births among younger generations or immigration increases.

Nationally, the U.S. population grew only by 0.7% to 323.1 million. That slowdown is due to an increase in deaths among baby boomers and a drop in births among younger generations, resulting in eight states losing overall population during the year.

The only saving grace for many communities, especially in the northeast, was immigration. In 34 states, international arrivals outpaced domestic arrivals (people who move from one state to another). Three states — Maryland, Massachusetts and Rhode Island — would have lost population if not for international arrivals. And New York's loss of 1,894 people in 2016 could have been staggering without the 118,478 foreigners who moved to the state.

Overall, the nearly 1 million immigrants who entered the country in 2016 were down from previous years, but still made up 45% of the nation's population growth. That figure could drop considerably under President-elect Donald Trump, who vowed to slow down legal and illegal immigration under his administration starting next month.

"The population is aging, the baby boomers are aging, but international migration has been fairly consistent," said Randy Capps, director of research for U.S. programs at the non-partisan Migration Policy Institute. "If we really did curtail immigration substantially, that would really slow population growth quite a bit."

The increase in the immigrant population came almost entirely through the legal immigration system. The federal government grants about 1 million green cards a year, and the immigrant population in the U.S. grew by nearly 1 million, according to the Census data. That backs up data from the Pew Research Center that has reported the number of undocumented immigrants in the U.S. has been flat, and starting to decline, over the past six years.

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Illinois lost more people than any other state (37,508), while West Virginia saw the biggest percentage drop (-0.54%). The other states that lost people were Connecticut, Mississippi, New York, Pennsylvania, Vermont and Wyoming. The big losses in the northeast, according to Capps, are a result of retirees moving south and an aging population that can't keep up with new births.

Illinois lost more people than any other state. Pennsylvania and New York also were among eight states that lost population between July 1, 2015, and July 1, 2016. The other states that lost people are Connecticut, Mississippi, Vermont, West Virginia and Wyoming.

Meanwhile, Utah proved to be the fastest-growing state in the country, with a rate of 2.03%. Capps said Utah's growing economy and its position as the heart of the Mormon Church, whose members have higher-than-average birth rates, contributed to that.

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“States in the South and West continued to lead in population growth,” Ben Bolender, chief of the Population Estimates Branch, said in a statement.

That includes big states, like Texas and Florida, as well as Nevada, Washington, Oregon and Colorado. Bolender said the demographic shifts mean 24% of Americans now live in the West, and 38% are concentrated in the South.

The state that’s long had the highest birth rate in the U.S., was followed closely by Nevada, Idaho, Florida, Washington, Oregon and Colorado in percentage-growth.

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In Utah, the growth was split nearly evenly between new births and migration of people attracted by the strong tech and financial industries, Pam Perlich with the University of Utah’s Kem C. Gardner Policy Institute told the Associated Press. The state is also home base for the growing Mormon church.

Top 10 States in Percentage Growth:

1. Utah (2.03%)

2. Nevada (1.95%)

3. Idaho (1.83%)

4. Florida (1.82%)

5. Washington (1.78%)

6. Oregon (1.71%)

7. Colorado (1.68%)

8. Arizona (1.66%)

9. District of Columbia (1.61%)

10. Texas (1.58%)

Bottom 10 States in Percentage Growth:

42. New Mexico (0.03%)

43. Kansas (0.02%)

44. New York (-0.01%)

45. Mississippi (-0.02%)

46. Pennsylvania (-0.06%)

47. Wyoming (-0.18%)

48. Connecticut (-0.23%)

49. Vermont (-0.24%)

50. Illinois (-0.29%)

51. West Virginia (-0.54%)