Year	Percent
1983	23.3089
1984	26.1233
1985	26.3234
1986	29.0981
1987	28.5704
1988	27.1251
1989	23.6631
1990	20.8924
1991	24.707
1992	24.3113
1993	26.8953
1994	25.119
1995	20.2901
1996	19.0503
1997	16.7498
1998	11.8254
1999	8.6742
2000	6.2251
2001	6.5041
2002	8.8173
2003	9.0292
2004	8.8956
2005	9.0871
2006	9.0063
2007	10.2484
2008	16.4628
2009	31.5672
2010	34.7628
2011	36.1248
2012	37.4498
2013	30.3439
2014	26.5857
2015	23.5494
2016	19.6727
2017	16.0278