Year	constant 2011 PPP $ per kg of oil equivalent
1990	3.85051495147767
1991	3.90157283489642
1992	3.9591316829377
1993	4.06645963594862
1994	4.27792507957765
1995	4.34666308033162
1996	4.44738278880614
1997	4.70078690923293
1998	4.8130921469645
1999	4.94984529600643
2000	5.18757605883861
2001	5.28779804982458
2002	5.3836248023224
2003	5.30029853900232
2004	5.27594210941027
2005	5.33681046109398
2006	5.45627294258862
2007	5.68277194512913
2008	5.87571488860513
2009	5.92439854010141
2010	5.86540572186829
2011	5.92811551804457
2012	6.05886624752487
2013	6.22816702352662
2014	6.46913754180696