Year	constant 2021 PPP $ per kg of oil equivalent
1990	5.70583248901617
1991	5.509534109914048
1992	5.4972133523434215
1993	5.246420770141475
1994	5.22169942243618
1995	5.20021375041511
1996	5.307877155437835
1997	5.382641671368425
1998	5.441362824056662
1999	5.375378249689672
2000	5.527289759961841
2001	5.548674204795511
2002	5.79653368455992
2003	5.761176627803101
2004	5.902678787839116
2005	6.123390872079285
2006	6.38592224156212
2007	6.513797148150546
2008	6.4491903109755295
2009	6.605616979129445
2010	6.797321865710157
2011	6.89454909864096
2012	6.939766467152296
2013	7.141855251752749
2014	7.350387470980333