The actual size and the origin of the undocumented immigrant population in the United States is uncertain and is difficult to ascertain because of difficulty in accurately counting individuals in this population. Figures from national surveys, administrative data and other sources of information vary widely. By all measures, the population of undocumented immigrants in the USA has declined substantially since 2007. The number of border apprehensions has substantially declined since 2000, the peak year, but more than doubled in the most recent fiscal year to approach 2007 levels.