Year	constant 2011 PPP $ per kg of oil equivalent
1990	5.44374003726368
1991	5.28022555362742
1992	5.37336791489185
1993	5.4970667097832
1994	5.6463179153184
1995	5.74400391035932
1996	5.99419952336273
1997	5.9989648551596
1998	6.22065441081165
1999	6.40195760800296
2000	6.49495464832967
2001	6.71205994435414
2002	6.76518234297811
2003	7.12628059500684
2004	7.30246216290013
2005	7.58398402084125
2006	7.78617498499159
2007	7.93434721195247
2008	7.79579236681194
2009	7.63529652335506
2010	7.9252321386516
2011	8.00105140150066
2012	8.03999341751844
2013	8.36022493502472
2014	8.44822708274958