Year	constant 2011 PPP $ per kg of oil equivalent
1995	4.12413221535975
1996	4.17566043884627
1997	4.27375089950488
1998	3.9299441521916
1999	4.42375105567255
2000	4.93219836567949
2001	5.27200098394062
2002	4.82507117315004
2003	5.08233891706431
2004	6.80837740645403
2005	7.60581544966845
2006	8.44115553552061
2007	9.17288962844927
2008	9.75698986798379
2009	6.70548561622306
2010	6.81228206289863
2011	6.97210885597581
2012	7.18115239695478
2013	7.46630849104557
2014	7.49345670017684