Year	constant 2021 PPP $ per kg of oil equivalent
1990	10.634494710895451
1991	10.310732507147511
1992	9.889465058959054
1993	9.471912119003807
1994	9.205503412133117
1995	9.235270575683694
1996	9.300143799143179
1997	9.406356125315934
1998	9.79663268066106
1999	9.947007463304452
2000	10.37766726049247
2001	9.858736605700583
2002	9.457723127312603
2003	9.676871068298123
2004	9.915909688087055
2005	9.823105975161317
2006	9.725885269130078
2007	9.733243393393751
2008	9.57655783913693
2009	9.194945340538956
2010	9.08332382043307
2011	9.392395159852914
2012	9.032680276001607
2013	9.295286574051207
2014	9.125853272899263