Year	constant 2021 PPP $ per kg of oil equivalent
1990	11.275735433638847
1991	11.896800004938287
1992	10.624699434663553
1993	10.795912945248222
1994	11.353625229893538
1995	11.865492729923078
1996	12.870951369520704
1997	13.288539539876101
1998	11.824176869643095
1999	12.556966105411778
2000	12.319648040361377
2001	12.207447526995768
2002	12.746990319430616
2003	13.379800291782956
2004	13.973828438229566
2005	14.15788477779021
2006	14.845036920603912
2007	15.19615391051645
2008	14.826664750883696
2009	13.647142182973713
2010	13.73002289091708
2011	15.268502081102946
2012	13.439945032552334
2013	14.119255893584382
2014	13.634386656029594