Data for "Resident Population" from 1900 to present are estimates as of July 1
Source: US. Bureau of the Census
US. Bureau of the Census, Resident Population in the Far West BEA Region [BEAFWPOP], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/BEAFWPOP/, October 10, 2015.