Year	constant 2011 PPP $ per kg of oil equivalent
1990	7.07633799292262
1991	7.58712235752745
1992	7.87943208914416
1993	7.8813767940961
1994	8.11380447846372
1995	8.16885208095849
1996	7.96653288799689
1997	8.1852472222529
1998	8.39809290940536
1999	8.76369692569
2000	8.97997579379025
2001	8.86623764640952
2002	9.06979347362843
2003	9.05308256077205
2004	9.09444490164806
2005	9.22645332259022
2006	9.30948416322926
2007	10.1543996325788
2008	10.1538670651851
2009	10.2320117925288
2010	10.1145653549639
2011	11.0321827264491
2012	11.0453114805346
2013	10.8932996769195
2014	11.553698928955
2015	11.5370289032116