Year	constant 2011 PPP $ per kg of oil equivalent
1990	7.44013372379147
1991	7.45046568747971
1992	7.59999802928645
1993	7.58600785752196
1994	7.81833965438069
1995	7.76187702918415
1996	7.65696517941052
1997	7.9585247184972
1998	8.15097913362573
1999	8.46015370973675
2000	8.73004072703591
2001	8.72590633337005
2002	8.86856569252759
2003	8.8073322958637
2004	8.95653771708128
2005	9.12848822272875
2006	9.41430485683621
2007	9.89320010328192
2008	10.0105003118907
2009	10.1698217794408
2010	9.98188781638452
2011	10.5654481269589
2012	10.6072357122109
2013	10.7611933270644
2014	11.3894352672151
2015	11.5399460357039