Year	constant 2011 PPP $ per kg of oil equivalent
1990	5.54684654927479
1991	5.79877949051378
1992	6.03593856063522
1993	6.01212989845203
1994	6.53887173193454
1995	6.71673020243119
1996	6.95419758177515
1997	6.97956131663312
1998	6.92689935085943
1999	7.05229425021965
2000	7.15825717710322
2001	7.12791549640942
2002	6.94486831280399
2003	7.07102330143625
2004	6.85129274066549
2005	6.96040583176548
2006	7.26652281281186
2007	7.23457602442927
2008	7.14905397488607
2009	6.90615619365835
2010	6.6200811454721
2011	7.03671058014327
2012	7.27686952783596
2013	7.67133389608052