Year	Percent
1983	23.8132
1984	26.1515
1985	26.343
1986	27.2807
1987	28.7344
1988	27.8594
1989	25.87
1990	23.439
1991	23.8066
1992	24.4964
1993	26.3852
1994	28.7094
1995	29.7773
1996	30.8112
1997	29.7469
1998	30.2418
1999	28.6221
2000	28.3749
2001	24.8135
2002	23.734
2003	23.6957
2004	21.0219
2005	21.6187
2006	19.2433
2007	18.3589
2008	18.8466
2009	23.2068
2010	26.8871
2011	27.1144
2012	33.7452
2013	39.0162
2014	41.2874
2015	38.7853
2016	36.459
2017	32.9876