Year	PPP $ per kg of oil equivalent
1990	2.1741494325366775
1991	2.1865853996545153
1992	2.164987070541726
1993	2.3644953786961476
1994	2.191467699208413
1995	2.2633622345463715
1996	2.469146143600225
1997	2.5002599531393503
1998	2.4939159131851203
1999	2.642253739889066
2000	2.738479111136288
2001	2.8583240739807803
2002	2.9336426459186233
2003	3.096393243447762
2004	3.307903649542865
2005	3.5407544316743618
2006	3.85202017246915
2007	4.285365928429275
2008	4.549539526575819
2009	4.880590572861319
2010	5.260598739666871
2011	5.366378330585615
2012	5.4363266247371556
2013	5.561969808106797