Year	constant 2011 PPP $ per kg of oil equivalent
1995	3.89707788893606
1996	3.79854022069211
1997	4.34320069069191
1998	4.44629063085533
1999	5.159111349579
2000	5.98244618573734
2001	5.49020061966643
2002	5.47343009748131
2003	5.79589069566516
2004	6.08808841637198
2005	6.95760405193948
2006	7.58401849277214
2007	7.76471358805067
2008	7.91948080087
2009	7.3264924648685
2010	9.25871384751559
2011	9.47336412509467
2012	9.74051851467724
2013	10.6693577700395
2014	10.9992272945245