Year	PPP $ per kg of oil equivalent
1990	3.8442049745273694
1991	3.9034293353342497
1992	4.060564511683133
1993	4.215753574086435
1994	4.39730140968894
1995	4.543157981299322
1996	4.78072242446152
1997	4.8583573860258955
1998	5.0606737328775235
1999	5.231535351790421
2000	5.428047530553818
2001	5.704117504249623
2002	5.843904485043816
2003	6.214858422989919
2004	6.528344457766305
2005	6.978593962004631
2006	7.371672626214691
2007	7.69180799877988
2008	7.776619226246668
2009	7.697859994940417
2010	8.020300931894756
2011	8.280937627827386
2012	8.693096618508488
2013	8.981185205763017
2014	8.934363645908357