Year	PPP $ per kg of oil equivalent
1990	4.399040180152701
1991	4.876071831820344
1992	5.179297467873306
1993	5.302267212020989
1994	5.571637397658857
1995	5.71616799770242
1996	5.668154418593521
1997	5.844885587436975
1998	6.067296324835248
1999	6.4440295612675165
2000	6.644375924144465
2001	6.740683753442279
2002	7.102187771633501
2003	7.322752900353875
2004	7.615887669562901
2005	7.780269056627953
2006	8.124353992020383
2007	9.106229506787153
2008	9.364372568773334
2009	9.712371336079212
2010	9.743594668671967
2011	10.993165713935863
2012	11.183955436853045
2013	11.421133419544427
2014	12.438688913617707
2015	12.471293972794895