Year	constant 2021 PPP $ per kg of oil equivalent
1990	4.930251957213419
1991	4.958158741555393
1992	4.949453638069846
1993	5.041842809190856
1994	5.255042916619361
1995	5.320942392451756
1996	5.421743517915295
1997	5.714935996521039
1998	5.828597908865686
1999	5.990457327392828
2000	6.275105537785081
2001	6.390990841181858
2002	6.498164514232695
2003	6.387497330723583
2004	6.350118529788214
2005	6.411316135679647
2006	6.539017129329532
2007	6.795298077073262
2008	7.011630483107729
2009	7.028041788233571
2010	6.939557660397319
2011	7.001264647670065
2012	7.144216505902352
2013	7.324505182135597
2014	7.552914644843283