Year	Percent
1983	23.0191
1985	18.5641
1987	15.6561
1988	14.0206
1989	12.4254
1990	10.2386
1991	10.2355
1992	7.706
1993	11.2907
1994	13.551
1995	11.5085
1996	11.2717
1997	9.2367
1998	8.2761
1999	6.6225
2000	4.6989
2001	4.2237
2002	4.3373
2003	6.6753
2004	7.8927
2005	8.0422
2006	6.0716
2007	5.6305
2008	5.3658
2009	7.1232
2010	8.8215
2011	10.4653
2012	11.7863
2013	13.487
2014	12.3818
2015	11.3292
2016	11.3782
2017	8.9593