Year	Percent
1983	28.9454
1984	30.3152
1985	29.7486
1986	26.9514
1987	28.6529
1988	23.4373
1989	20.152
1990	19.1588
1991	17.1115
1992	15.1766
1993	19.6235
1994	23.3698
1995	23.6854
1996	24.4055
1997	25.7011
1998	23.0375
1999	22.4307
2000	18.1563
2001	16.6261
2002	15.1687
2003	17.5009
2004	19.5105
2005	22.0583
2006	22.5659
2007	20.882
2008	18.7203
2009	22.4903
2010	22.3661
2011	18.7426
2012	18.8708
2013	22.4737
2014	22.3346
2015	20.0483
2016	18.1553
2017	18.0386