Year	US$ per liter
1991	0.39
1992	0.39
1995	0.43
1998	0.385
2000	0.5
2002	0.43
2004	0.79
2006	0.98
2008	1.145
2010	1.125
2012	1.3450000000000002
2014	1.185
2016	0.82