a lack of younger immigration has caused the median age of many of these counties to increase. In 24 counties, at least 20% of the population is over the age of 65, compared with a national rate of 12.8%. The effect of rural flight has not been spread evenly through South Dakota, however. Although most rural counties and small towns have lost population, the Sioux Falls area, the larger counties along Interstate 29, the Black Hills, and many Indian reservations have all gained population. As the reservations have exercised more sovereignty, some Sioux have returned to them from urban areas. Lincoln County near Sioux Falls was the seventh fastest-growing county (by percentage) in the United States in 2010. The growth in these areas has compensated for losses in the rest of the state. South Dakota's total population continues to increase steadily, albeit at a slower rate than the national average. Religion According to the Public Religion Research Institute in 2020, 73% of the adult population were Christian. Per the Pew Research Center's separate 2014 study, the largest religious denominations by number of adherents as a percentage of South Dakota's population in 2014 were the Catholic Church with 22 percent, Evangelical Protestants with 25 percent, and Mainline Protestants with 32 percent. Together, all kinds of Protestants accounted for 57 percent. Those unaffiliated with any religion represented 18 percent of the population. The breakdown of other religions is <1% Muslim, <1% Hindu and 1% Buddhist. The largest denominations by number of adherents in 2010 were the Roman Catholic Church with 148,883 members; the Evangelical Lutheran Church in America (ELCA) with 112,649 members; and the United Methodist Church (UMC) with 36,020 members. (The ELCA and UMC are specific denominations within the broader terms 'Lutheran' and 'Methodist', respectively.) Economy The current-dollar gross state product of South Dakota was $39.8 billion as of 2010, the fifth-smallest total state output in the U.S. The per capita personal income was $38,865 in 2010, ranked 25th in the U.S., and 12.5% of the population was below the poverty line in 2008. CNBC's list of "Top States for Business for 2010" has recognized South Dakota as the seventh best state in the nation. In July 2011, the state's unemployment rate was 4.7%. The service industry is the largest economic contributor in South Dakota. This sector includes the retail, finance, and health care industries. Citibank, which was at one time