Based on a comparison of 97 countries in 2015, Kuwait ranked the highest in oil rents as a percentage of GDP with 38.5% followed by Iraq and Saudi Arabia. On the other end of the scale was South Korea with < 0.001%, Slovenia with < 0.001% and Japan with < 0.001%.
Average oil rents as a percentage of GDP reached 0.818% in 2015 in the World according to EIA. This is 141 % less than in the previous year and -160 % less than 10 years ago.
Historically, average oil rents as a percentage of GDP reached an all time high of 4.27% in 1980 and an all time low of 0.183% in 1971. The average annual growth amounted to 2.96 % since 1970.
Data for more countries are available at Oil Rents (As % of GDP) indicator page.