Year	PPP $ per kg of oil equivalent
1990	5.901378237321623
1991	6.031545442429569
1992	6.112641265673138
1993	6.456890267056284
1994	6.397035993445176
1995	6.415560289682024
1996	6.818614359080874
1997	6.797655596080261
1998	6.928507359440021
1999	6.933430211068937
2000	7.186653327088793
2001	7.499788653235954
2002	7.84190448761829
2003	7.933383995210198
2004	8.072985457308658
2005	8.490791166061538
2006	9.617793393748034
2007	10.212751572190152
2008	10.99126003521129
2009	11.637062424111564
2010	11.548902952636062
2011	11.84822055093107
2012	11.821067623352087
2013	12.91524411495671
2014	13.608616110784094
2015	13.580224391318678