The Longley data has become the workhorse to illustrate several econometric problems, including multicollinearity. The data are reproduced in Table A. The data are time series for the years 1947–1962 and pertain to Y = number of people employed, in thousands; X1 = GNP implicit price deflator; X2 = GNP, millions of dollars; X3 = number of people unemployed in thousands, X4 = number of people in the armed forces, X5 = noninstitutionalized population over 14 years of age; and X6 = year, equal to 1 in 1947, 2 in 1948, and 16 in 1962.