Create a sample of incumbents with redistribution preference in the current and next elections

[mkudamatsu]

Input:
nameid_year_smallgov.dta
the output from issue #8

Method:
Drop Upper House election candidates
Drop district-year with the number of incumbents being either 0 or 2+
Extract smallgov in the next election (leave it missing for the 2014 elections; the 2017 election data is soon to be available)
Create the indicator of running for office in the next election
Keep the indicator of winner

Output:
Key district year
Variables
smallgov_now
smallgov_next
run_next
winner
Foreign key
nameid