Premise: Clark County is a county in the U.S. state of Nevada. As of the 2010 census, the population was 1,951,269, with an estimated population of 2,114,801 in 2015. It is by far the most populous county in Nevada, accounting more than two-thirds of its residents. Las Vegas, Nevada's most populous city, has been the county seat since the county was established.
Hypothesis: The estimated population of Clark County in 2015 was higher than in the 2010 census because of mass immigration.