Year	PPP $ per kg of oil equivalent
1990	2.821149399009969
1991	2.966960857524762
1992	3.140982494873407
1993	3.2822308248311995
1994	3.4876930605239966
1995	3.5975305785217335
1996	3.786427799314072
1997	4.000325104858195
1998	4.091733005311816
1999	4.20955295901973
2000	4.458595274268023
2001	4.619948432037449
2002	4.746728799309821
2003	4.81425931012659
2004	4.988094014927841
2005	5.237723961957127
2006	5.5882567676295825
2007	5.9497825115179905
2008	6.26706198479586
2009	6.367668390077738
2010	6.477706144577557
2011	6.735173725231712
2012	6.975642391584094
2013	7.2375869620473585
2014	7.420527401336666