Year	Percent
1960	40.85155
1961	35.37634
1962	37.8926
1963	35.90909
1964	35.35599
1965	43.51978
1966	43.28063
1967	40.22606
1968	41.76471
1969	45.92704
1970	46.52501
1971	44.16
1972	46.64298
1973	48.986
1974	51.13734
1975	47.66231
1976	50.56696
1977	56.20353
1978	60.7119
1979	59.9674
1980	57.92028
1981	53.08429
1982	57.34115
1983	59.7306
1984	49.24287
1985	44.89255
1986	47.77539
1987	50.60054
1988	49.61301
1989	48.96748
1990	44.84762
1991	45.51048
1992	44.77906
1993	36.93086
1994	37.79059
1995	38.77859
1996	38.95508
1997	35.7816
1998	36.01411
1999	35.77634
2000	35.27152
2001	35.2418
2002	35.14838
2003	36.54541
2004	37.95243
2005	37.45301
2006	28.3331
2007	27.29411
2008	29.4081
2009	30.99338
2010	28.03874
2011	23.6637
2012	22.13115
2013	20.36984
2014	19.58377
2015	19.98265
2016	20.84429
2017	19.56171
2018	18.13655
2019	17.32323
2020	18.85378
2021	19.65747
2022	19.56548