Year	constant 2011 PPP $ per kg of oil equivalent
1990	9.21658467628719
1991	9.14870816599432
1992	9.39432247084995
1993	9.41831857432388
1994	9.6661505655359
1995	9.35711911489251
1996	9.77540761408137
1997	9.92567445503494
1998	10.1550198327368
1999	10.1418964740956
2000	10.6353547422237
2001	10.2309633636018
2002	10.1767825040421
2003	9.7446545986227
2004	10.0175980661828
2005	9.58937276210993
2006	9.79715601920777
2007	10.0875190245297
2008	10.3077257505347
2009	9.75056885890406
2010	10.5501997552915
2011	10.4092684413814
2012	10.3331004028858
2013	10.4517660222532
2014	10.9802602837717
2015	11.3807332845901