WASHINGTON -- West Virginia was one of just two states in the nation to lose population between the middle of 2012 and the middle of 2013, according to estimates released by the U.S. Census Bureau on Monday.The state's estimated population went from 1,856,680 on July 1, 2012, to 1,854,304 on July 1, 2013 -- an estimated decrease of 2,376 residents.Maine was the only other state with a decline in estimated population, and its drop was fewer than 200 residents.North Dakota's population expanded at nearly twice the rate of the next-fastest-growing state, according to the Census estimates. That boom was driven by the state's thriving oil and gas industry.Population estimates are eagerly watched by state officials since they determine the flow of money into many federal programs and, ultimately, representation in Congress. The number of representatives each state has in the House of Representatives gets readjusted each decade.At least one national political website, Real Clear Politics, predicted Monday that West Virginia would lose one of its three seats in the U.S. House in 2020, given current population trends.West Virginia has never had fewer than three U.S. House members in its 150-year history.The state had six seats in the House for five decades in the middle of the 20th century, but lost one after the 1960 Census, another after the 1970 Census and another after the 1990 Census.Nationwide, the West and South continued to drive population growth nationally, accounting for more than four in five new residents, while growth in the Northeast and Midwest continued to lag behind.California (38,332,521) and Texas (26,448,193) remain the nation's most populous states, with New York (19,651,127) narrowly maintaining its third position over Florida (19,552,860) as of July 1. The Sunshine State will soon surpass New York, if it hasn't already, because its population grew three times faster, according to the Census estimates, which are based on data measuring births, deaths and migration.California's population growth again outpaced the national trend, with an increase of 332,643 year to year, or 0.9 percent. Texas actually saw a greater raw population increase, however, expanding by 387,397.North Dakota's population stood at 723,393 on July 1, according to the census data, a 3.1 percent increase from 2012. Since the 2010 census, North Dakota's population has grown 7.6 percent, far outpacing the national growth rate of 2.4 percent during that period.Population in the District of Columbia also grew at a sustained clip, rising 2.1 percent year to year to 646,449. Utah grew next fastest, at a rate of 1.6 percent, followed by Colorado (1.5 percent), Texas (1.5 percent) and Nevada (1.3 percent).Pennsylvania, New Mexico, Vermont and Illinois posted the slowest population growth, all at or near a tenth of a percentage point year to year.The national population stood at 316,128,839 on July 1, an increase of 2.3 million, or 0.7 percent from the previous year. Population growth in the South accounted for half of all population growth nationally, though the West grew at a slightly faster pace in the last year.