Year	constant 2011 PPP $ per kg of oil equivalent
1992	9.70739922484072
1993	9.33063194668425
1994	8.62470393930862
1995	8.82169575806615
1996	9.02441942493267
1997	9.15478154585621
1998	8.30629504238413
1999	7.60106229747402
2000	7.66088250764348
2001	7.23043112210178
2002	7.24185806877809
2003	7.96939246077892
2004	8.27252886042152
2005	8.09669818422672
2006	8.91541831300798
2007	9.23314905106651
2008	8.65513523561184
2009	7.35221813974578
2010	7.02887353241601
2011	7.63333581943486
2012	7.08631514858081
2013	7.63107107791846
2014	7.90820468362907