These poverty numbers are five-year averages from the American
Community Survey, and represent the total number of people under 18
years who live in poverty, divided by the child population for which poverty status is known.
The U.S. Census Bureau website has information on federal poverty thresholds by year.
This information is taken from Table S1701 from the American Community
Survey. The American Community Survey can be accessed here: http://factfinder2.census.gov/.