Year	Percent
1960	31.54896
1961	30.22594
1962	30.42222
1963	29.81553
1964	35.57969
1965	31.11177
1966	31.22353
1967	27.60105
1968	29.09316
1969	32.34157
1970	38.78836
1971	39.87974
1972	38.48026
1973	32.99328
1974	28.88681
1975	53.69499
1976	46.52715
1977	52.46283
1978	76.88172
1979	76.23511
1980	56.35152
1981	52.96367
1982	58.66667
1983	46.74435
1984	53.34608
1985	57.10949
1986	55.68862
1987	50.74587
1988	52.59477
1989	48.84127
1990	45.33526
1991	41.53357
1992	36.15164
1993	32.09458
1994	34.25449
1995	37.40955
1996	44.14039
1997	44.80554
1998	43.30148
1999	39.01484
2000	47.60582
2001	48.48418
2002	49.0758
2003	59.11633
2004	57.86935
2005	58.655
2006	56.11666
2007	54.49131
2008	51.93617
2009	52.34761
2010	57.309
2011	56.33009
2012	60.50567
2013	72.32477
2014	62.91994
2015	67.60207
2016	62.80309
2017	59.50938