Year	Percent
1983	17.5202
1984	16.9591
1985	16.5976
1986	17.0314
1987	15.0382
1988	11.9067
1989	9.2987
1990	9.2522
1991	11.4471
1992	11.6635
1993	13.4486
1994	12.7978
1995	12.5811
1996	11.3782
1997	11.1823
1998	10.6399
1999	10.3553
2000	10.4015
2001	8.6837
2002	8.7665
2003	9.4664
2004	9.726
2005	10.9927
2006	12.0211
2007	12.5469
2008	12.7804
2009	16.122
2010	17.5981
2011	18.5364
2012	18.2107
2013	18.1269
2014	14.7921
2015	12.928
2016	11.0859
2017	10.5872