Year	Percent
1992	12.151
1993	12.636
1994	13.111
1995	12.142
1996	11.008
1997	9.2667
1998	8.3585
1999	11.5468
2000	14.5887
2001	16.9546
2002	19.2264
2003	18.895
2004	18.4908
2005	16.5869
2006	12.9508
2007	8.9942
2008	6.4301
2009	7.7588
2010	9.324
2011	9.0087
2012	9.4192
2013	9.686
2014	8.4981
2015	7.3308
2016	6.1077
2017	4.8711