Year	constant 2011 PPP $ per kg of oil equivalent
1990	13.2816526321785
1991	12.9626128642791
1992	12.8996739661165
1993	13.2142483252694
1994	13.2622581980942
1995	13.518903605908
1996	13.3311496615289
1997	13.4069236660654
1998	13.642610543956
1999	13.8491314831595
2000	14.5883179025646
2001	13.9160947375874
2002	14.2990622492602
2003	14.2457844000094
2004	14.5882876229592
2005	15.1282011800737
2006	15.0676178131366
2007	16.4972524021337
2008	16.216922215918
2009	15.7403490975911
2010	16.6883733851576
2011	17.5282616433108
2012	17.5312441893096
2013	17.1107036399577
2014	18.6990884515888
2015	19.365965477856