Year	constant 2011 PPP $ per kg of oil equivalent
1990	11.9567068072496
1991	11.168049258357
1992	11.1067293175108
1993	10.8348571238246
1994	11.1395840311333
1995	11.0822198526073
1996	11.9147393163703
1997	11.7551878324352
1998	11.9378161774971
1999	11.5409994533655
2000	11.795545068474
2001	12.125709308168
2002	11.9719032174026
2003	12.0762727235258
2004	12.4411619261418
2005	12.6529937712882
2006	12.0152214281909
2007	11.7045239006164
2008	11.8410032632175
2009	11.0038492843222
2010	11.5962610394477
2011	11.4377357580382
2012	10.7568241086926
2013	10.679456762777
2014	10.2061486866368