Year	constant 2021 PPP $ per kg of oil equivalent
1990	26.30513777170811
1991	25.79664214674623
1992	26.795587439881253
1993	26.368738338156753
1994	28.894986810883296
1995	26.31643349477119
1996	29.125111004089028
1997	30.245981881049254
1998	31.349091201134506
1999	31.02232722856333
2000	33.608197297150525
2001	31.121393853175448
2002	32.31125826961963
2003	27.602160379620184
2004	26.897346480353416
2005	26.788470630255546
2006	22.162092040424042
2007	23.301755216285777
2008	23.149332415682053
2009	22.63267864242717
2010	22.841780721823717
2011	17.53346302180072
2012	16.8203584151055
2013	16.27954451696207
2014	17.341477307271646