Year	constant 2011 PPP $ per kg of oil equivalent
1990	5.62997440989975
1991	4.82700426058544
1992	4.67741276816191
1993	4.46847216237011
1994	4.35842131157992
1995	4.41373281635428
1996	4.54024047337982
1997	4.58868981875992
1998	5.23559702174023
1999	5.48921387021645
2000	5.43391922199578
2001	5.39587758996261
2002	5.54743932829379
2003	5.26639526042055
2004	5.88219858268298
2005	6.07219669313107
2006	6.41375164116982
2007	6.61887074738793
2008	6.694563315879
2009	6.80708755435547
2010	6.80345227800057
2011	6.76102867460647
2012	6.82462626307848
2013	7.05105221930457
2014	7.25467149551311