Year	Percent
1983	14.2677
1984	15.2691
1985	15.3206
1986	16.9858
1987	16.6234
1988	17.4074
1989	17.2843
1990	15.6738
1991	15.7221
1992	13.8719
1993	14.8332
1994	15.3111
1995	16.1032
1996	16.225
1997	16.3994
1998	16.5356
1999	16.2706
2000	14.8582
2001	13.031
2002	12.6101
2003	11.9451
2004	10.2209
2005	10.0439
2006	8.774
2007	7.8401
2008	8.4957
2009	9.2224
2010	9.598
2011	9.5439
2012	11.8259
2013	13.0669
2014	13.7982
2015	12.6939
2016	12.7744
2017	12.3864