Year	constant 2011 PPP $ per kg of oil equivalent
1990	2.2254801222838
1991	2.30889649110255
1992	2.31225419862342
1993	2.39990765779763
1994	2.47113733423605
1995	2.62687980534657
1996	2.37970119155747
1997	2.71434991585308
1998	2.52761190399151
1999	2.33848833704181
2000	2.36140990690236
2001	2.20268317149705
2002	2.18492136153455
2003	2.23580017495747
2004	2.29921074806065
2005	2.12687268590037
2006	2.15797653396123
2007	2.12537785502446
2008	2.26329996900767
2009	2.14064033628584
2010	2.06899986607293
2011	2.09667726972676
2012	2.17851371612291
2013	2.1822395404993
2014	2.16462524695682