Incumbent share of the two-party presidential vote
= 1 if Democratic incumbent at election time; -1 if a Republican incumbent
= 1 if incumbent is running for election and 0 otherwise
number of terms incumbent administration in power
= 1 for elections of 1920, 1944, and 1948 and 0 otherwise.
growth rate GDP in first three quarters of the election year
growth rate in first 15 quarters of admin, 0 for 1920, 1944, 1948
number of quarters in first 15 with real GDP per capita growth > 3.2