Variable Description Presidentialism Binary variable for presidentialism: presidentialism (=1); other (parliamentarism & mixed =0). PR system Binary variable for proportional representation: PR (=1); other (SMD & mixed =0). Log PPP GDP Natural logarithm of the expenditure-based real gross domestic product (GDP) in millions of 2011 US dollars at chained purchasing power parity (PPP) rates. Log Rent Natural logarithm of the World Bank's indicator "total natural resources rents (% of GDP)." Democratic Stock Democratic stock variable based on the coefficient for democratic stock suggested by Gerring, et al. (2005). Ethnic Fractionalization Ethnic fractionalization index based on the Fearon's research (2003).