Year	constant 2021 PPP $ per kg of oil equivalent
1990	5.139592186609091
1991	4.975698340239958
1992	4.963005602501237
1993	4.707151753517596
1994	4.665940677285405
1995	4.666022599238727
1996	4.8173278091489244
1997	4.896494121939775
1998	4.922478327378513
1999	4.916668632423875
2000	5.042607173192852
2001	5.061596276265075
2002	5.227946141177674
2003	5.147421292156586
2004	5.184382994730043
2005	5.445195234308691
2006	5.704988604618472
2007	5.834325379325938
2008	5.744413382662687
2009	5.736322446297101
2010	5.975643803712322
2011	6.1073786713013885
2012	6.150730740299847
2013	6.2768791483992095
2014	6.325952097768904