Year	constant 2011 PPP $ per kg of oil equivalent
1990	3.37528642252529
1991	3.68166162966325
1992	3.64844526827275
1993	3.43980104108517
1994	3.51448622908462
1995	3.51550500145518
1996	3.411820022226
1997	3.61311302128598
1998	3.63654910915451
1999	3.36509914547819
2000	3.15108927914824
2001	3.38389094170325
2002	3.30941952335289
2003	3.38408736417895
2004	3.69559599966109
2005	3.8675865627118
2006	3.28635542105671
2007	3.02618914008374
2008	2.73175480267504
2009	2.4543131110682
2010	2.35777147512636
2011	2.24518882904523
2012	2.32991716479978
2013	2.33092947122784
2014	2.38750844755564
2015	2.53007022637734