Year	Percent
1983	10.2347
1984	9.6066
1985	8.9591
1986	6.7879
1987	7.4087
1988	6.3284
1989	5.2146
1990	4.4417
1991	5.2021
1992	5.4455
1993	7.6472
1994	9.4477
1995	8.7202
1996	10.5005
1997	11.9591
1998	10.8529
1999	9.8953
2000	9.4944
2001	8.9919
2002	11.1017
2003	13.6722
2004	15.3757
2005	16.795
2006	14.7887
2007	12.6134
2008	11.0463
2009	12.476
2010	10.7473
2011	9.194
2012	8.6864
2013	8.4674
2014	8.3457
2015	7.8918
2016	7.8463
2017	7.5981