Year	PPP $ per kg of oil equivalent
1990	2.1170936354396255
1991	2.084841931254357
1992	2.102559974334532
1993	2.238811032979858
1994	2.473982638530465
1995	2.6218948224032963
1996	2.795322491702996
1997	2.999590832940745
1998	3.2620698132420025
1999	3.275090635048808
2000	3.4556213511546123
2001	3.584233437026341
2002	3.821099190338405
2003	4.088436976640733
2004	4.457161976690065
2005	4.748041092059006
2006	5.451812345005502
2007	6.39286243447483
2008	6.966528686101642
2009	7.429110573869379
2010	7.680708574128427
2011	8.170267283231695
2012	8.762241826032076
2013	8.949126776929816
2014	9.863137109309871
2015	10.005819437347764