Year	constant 2015 US$
1988	8550000
1989	16600000
1990	14990000
1991	427730000
1992	526880000
1993	376590000
1994	209400000
1995	211910000
1996	273050000
1997	215600000
1998	352380000
1999	655060000
2000	458610000
2001	395840000
2002	425830000
2003	414120000
2004	330430000
2005	333520000
2006	335260000
2007	287120000
2008	314990000
2009	316460000
2010	330650000
2011	321890000
2012	313090000
2013	238460000
2014	247210000
2015	333490000
2016	168600000
2017	154900000