Year	Percent
1988	3.56068
1989	14.14641
1990	14.74273
1991	12.22927
1992	4.4575
1993	6.7559
1994	6.27119
1995	4.49388
1996	5.46551
1997	8.50375
1998	8.54264
1999	9.64374
2000	4.18518
2001	3.10075
2002	2.16715
2003	5.74279
2004	0.67834
2005	0.27535
2006	0.30553
2007	0.45596
2008	0.73532
2009	0.29508
2010	0.56628
2011	2.62239
2012	3.39365
2013	3.41413
2014	4.32786
2015	4.12577
2016	2.82687