Variable Descriptions for the approval.asc dataset.  Located at:
http://www.courses.fas.harvard.edu/~gov1000/Data/approval.asc

Variable Name: Description

Date: YYYY.MM 1953.01 to 2000.06
administration: administration number from 1 to 9 
approval: monthly average approval rating
lagApproval: lagged approval, the approval rating the previous month
unrate: civilian adult unemployment rate
inflation: inflation rate based on year-on-year changes in the
           seasonally adjusted CPI all urban workers
kennedy: 1 if Kennedy administration, 0 otherwise
johnson: 1 if Johnson administration, 0 otherwise 
nixon:   1 if nixon administration, 0 otherwise 
ford:    1 if ford administration, 0 otherwise 
carter:  1 if Carter administration, 0 otherwise 
regan:   1 if Regan administration, 0 otherwise 
bush:    1 if Bush administration, 0 otherwise 
clinton: 1 if Clinton administration, 0 otherwise 
Eisenhower: 1 if Eisenhower administration, 0 otherwise 
inflationMonthly: inflation rate based on month-on-month changes in the
                  seasonally adjusted CPI all urban workers