Year	Percent
1990	0.638
1991	1.354
1992	3.072
1993	6.183
1994	7.727
1995	8.338
1996	8.967
1997	9.6876
1998	9.0525
1999	9.9387
2000	11.9706
2001	11.5904
2002	7.5295
2003	8.9627
2004	8.1342
2005	6.8185
2006	5.4021
2007	4.1703
2008	4.8239
2009	9.6854
2010	12.7346
2011	11.4979
2012	9.2017
2013	8.2171
2014	7.1879
2015	5.8174
2016	5.6275
2017	5.3377