Year	PPP $ per kg of oil equivalent
1990	3.365354224807873
1991	3.465672431008602
1992	3.4973343336439515
1993	3.5321180007196813
1994	3.550338323698511
1995	3.6669965255760975
1996	3.8503028118777225
1997	4.040458186729965
1998	4.127504495055071
1999	4.213055591032651
2000	4.451514653761
2001	4.599996349816587
2002	4.738924445753953
2003	4.894532830841304
2004	5.264403281329905
2005	5.662731594268087
2006	6.007168425408587
2007	6.448150766718043
2008	6.747542354983856
2009	6.7616459095249715
2010	7.019697176880827
2011	7.226721051051164
2012	7.3928228066111705
2013	7.635786311178967
2014	7.925544201843123