Year	constant 2011 PPP $ per kg of oil equivalent
1990	8.71752054050127
1991	7.7401616753936
1992	7.64395430619554
1993	7.76837678692296
1994	8.52778595442572
1995	8.6566265402991
1996	8.60558966586378
1997	7.93553531306023
1998	7.73371092341081
1999	8.1030949068596
2000	7.73503197828778
2001	7.47101279948365
2002	7.61741912034403
2003	7.52138068255489
2004	7.46829787516148
2005	7.25211995186989
2006	7.61534932874995
2007	7.39243828267866
2008	7.41350931499004
2009	7.68422209675455
2010	8.08611686166428
2011	8.16535523647021
2012	8.46369488690438
2013	7.85718071968964
2014	8.15309086749179