Year	Percent
1976	32.38146
1977	33.12572
1978	33.45487
1979	34.72774
1980	40.3932
1981	43.63912
1982	40.62064
1983	35.79984
1984	39.07944
1985	39.65868
1986	28.30193
1987	33.06847
1988	43.44652
1989	56.05365
1990	59.83713
1991	57.39013
1992	50.2293
1993	50.33658
1994	47.85117
1995	51.72237
1996	52.87237
1997	49.24522
1998	44.79478
1999	43.31516
2000	41.8292
2001	42.13387
2002	47.50544
2003	47.37213
2004	52.56668
2005	53.33228
2006	54.4684
2007	54.86421
2008	57.79768
2009	46.43585
2010	48.256
2011	47.65491
2012	46.24668
2013	42.35182
2014	43.33313
2015	37.58781
2016	35.14247
2017	35.57727