Year	constant 2021 PPP $ per kg of oil equivalent
1990	12.972862629363988
1991	12.99161425362214
1992	13.029618712397816
1993	14.433447528771271
1994	12.892643950847559
1995	12.97333167663547
1996	13.172580888409035
1997	12.85355591950823
1998	12.978958307834246
1999	13.21938862195928
2000	12.874573756996053
2001	13.601535604181949
2002	13.393376507326138
2003	13.960355055501736
2004	15.832207293825164
2005	15.936359782103342
2006	16.805006135789778
2007	17.748495688058664
2008	18.267076703791
2009	18.79035962246295
2010	19.370982573393917
2011	19.6167837360605
2012	19.082724275752952
2013	21.229516017291065
2014	22.7008424500675