Population data was obtained at the county level from the Texas
Department of State Health Services (TDSHS,
http://www.dshs.state.tx.us/chs/popdat/default.shtm).
TDSHS estimates were used over US Census values so that population data could be
compared with other datasets (which were collected in years the US Census did
not occur - 1997, 2002, and 2007) in the Texas Land Trends study. TDSHS and US
Census data may vary slightly.