Year	constant 2015 US$
1991	148580000
1992	15690000
1993	22160000
1994	72240000
1995	76460000
1996	160340000
1997	173750000
1998	275470000
1999	210330000
2000	222840000
2001	197470000
2002	251750000
2003	326180000
2004	290390000
2005	238350000
2006	188150000
2007	213560000
2008	329950000
2009	284480000
2010	199500000
2011	178050000
2012	118420000
2013	80540000
2014	79520000
2015	77460000
2016	63580000
2017	58250000