Year	constant 2011 PPP $ per kg of oil equivalent
1990	6.1446772024614
1991	5.7795223158452
1992	5.62935819556384
1993	5.69831836913932
1994	5.8265139457724
1995	5.99886623148445
1996	6.2642470446149
1997	6.22261470951221
1998	6.41791311531182
1999	6.7723987869631
2000	6.88026247617843
2001	7.02270494616937
2002	6.82694586316384
2003	6.83867486563315
2004	6.88739114829438
2005	7.06765791846161
2006	7.43048184741334
2007	7.68005617977777
2008	7.85619227179341
2009	7.55314936201368
2010	7.81950909921846
2011	8.03543257662278
2012	7.96259208095714
2013	7.80349189035428
2014	7.85677260073728