Year	constant 2011 PPP $ per kg of oil equivalent
1995	7.53686719115194
1996	7.73050234758613
1997	7.79533592649804
1998	7.68597397246841
1999	7.70672915894515
2000	8.30726252689269
2001	8.27942622729119
2002	8.470547390388
2003	8.33644911266274
2004	8.66654039507396
2005	8.88923876369648
2006	9.37407426861136
2007	9.4913132304296
2008	9.93373645851058
2009	9.52388942767382
2010	9.49811392535899
2011	9.69828391408265
2012	10.0670730682051
2013	10.2322749897835
2014	10.7303540713322