Year	Percent
1983	34.9201
1984	37.9012
1985	39.1348
1986	40.2537
1987	39.7088
1988	39.4823
1989	38.5493
1990	35.3591
1991	33.4938
1992	32.9815
1993	34.9045
1994	35.7195
1995	38.2263
1996	39.6844
1997	40.5858
1998	38.4042
1999	38.3337
2000	35.2896
2001	31.5657
2002	31.5487
2003	30.8838
2004	28.9171
2005	27.5877
2006	25.4426
2007	23.3175
2008	24.6541
2009	28.5261
2010	29.4158
2011	32.0964
2012	37.5822
2013	41.457
2014	44.6549
2015	42.6095
2016	39.62
2017	37.2857