Year	PPP $ per kg of oil equivalent
1990	2.152124538516742
1991	2.2670872602404466
1992	2.395160998291077
1993	2.5568141246339597
1994	2.794322657663912
1995	2.925798488613099
1996	3.0696617888521978
1997	3.311710789123549
1998	3.4490440630529595
1999	3.5920937555311157
2000	3.850309170182348
2001	4.016337300442073
2002	4.173303304569672
2003	4.206600963867516
2004	4.30530847293449
2005	4.511037681261307
2006	4.838440649958448
2007	5.183177499763132
2008	5.556527336552536
2009	5.6790553569244056
2010	5.707868323453805
2011	5.930844924790903
2012	6.175169575528535
2013	6.406253991106306
2014	6.596038669335818