Year	constant 2011 PPP $ per kg of oil equivalent
1990	11.9123684447407
1991	12.4132248736146
1992	12.6947761353746
1993	12.5151620933213
1994	13.568416954396
1995	13.6422063221491
1996	13.6163067730778
1997	14.9777891287831
1998	14.1835418133351
1999	13.5124929591406
2000	13.9167824209985
2001	14.5092280598083
2002	15.1996475199944
2003	16.1530560602575
2004	15.3251587337228
2005	15.3692068166785
2006	17.0204843208907
2007	17.0703886066619
2008	17.7610531665791
2009	17.1277709950206
2010	15.6674876484564
2011	16.3665383845654
2012	16.1422103509965
2013	17.1514009748143
2014	15.0431929730403