Fig. 4.
Partial regression plots of the response of log GDP per capita 1997 to geography and biogeography and institutions. Geography and biogeography is the sum of the variables log geography, (T - 
) and (T - 
)2, after each variable was weighted by its estimated coefficient in regression model 6 (Table 3). The vertical axes show variation in the dependent variable log 1997 GDP per capita after controlling for institutions (Left) or geography plus biogeography (Right). The horizontal axes show variation in geography plus biogeography after controlling for institutions (Left) and variation in institutions controlling for geography plus biogeography (Right).