Statistics on Democracy and GDP (National Income)

There are at least two types of links between democracy and GDP. The wealthier a country, the more likely it will be – or turn out to be – a democracy:

democracy and income correlation

(source)

(source, scatter plot covers all countries with population larger than 1 million and with fuel exports less than 50% of export revenues)

Also, once a country is a democracy, the election outcomes in that country depend heavily on economic growth:

(source)