Year	US$ per liter
1992	0.395
1995	0.395
1998	0.365
2000	0.5249999999999999
2002	0.455
2004	0.6100000000000001
2006	0.735
2008	0.66
2010	0.985
2012	1.145
2014	0.965
2016	0.76