Year	Percent
1966	43.57733
1967	47.18985
1968	50.99335
1969	51.09171
1970	40.90886
1971	37.18131
1972	40.75574
1973	42.38109
1974	43.7155
1975	43.6146
1976	46.35489
1977	47.51712
1978	59.88797
1979	63.25521
1980	63.59847
1981	66.75703
1982	59.63816
1983	62.48225
1984	64.78919
1985	53.91662
1986	56.09832
1987	59.2869
1988	58.45328
1989	65.27742
1990	71.58268
1991	34.66403
1992	36.85038
1993	36.43791
1994	28.67646
1995	35.50115
1996	29.15572
1997	25.3853
1998	28.56539
1999	28.01594
2000	30.56115
2001	25.10847
2002	32.48557
2003	37.76501
2004	48.76014
2005	49.58511
2006	47.2124
2007	42.06633
2008	39.80311
2009	41.91357
2010	42.71623
2011	41.06556
2012	44.27735
2013	41.09331
2014	48.53051
2015	50.42119
2016	41.91754
2017	39.97758