Year	Percent
1960	51.42784
1961	51.50305
1962	49.88108
1963	44.84591
1964	41.82871
1965	41.94125
1966	35.13252
1967	34.85796
1968	32.54023
1969	34.50956
1970	38.16491
1971	38.81777
1972	38.53805
1973	39.84134
1974	39.60102
1975	35.81041
1976	34.37769
1977	35.60432
1978	34.7435
1979	32.12931
1980	29.91354
1981	33.37992
1982	34.10534
1983	31.19112
1984	28.60645
1985	31.46633
1986	34.51775
1987	31.61163
1988	39.37288
1989	37.36901
1990	39.01959
1991	40.18435
1992	38.54295
1993	39.90007
1994	34.5307
1995	37.28028
1996	42.38485
1997	45.04225
1998	44.39459
1999	43.2655
2000	40.68217
2001	35.78077
2002	37.66274
2003	38.41661
2004	34.00608
2005	33.19992
2006	31.82011
2007	35.66751
2008	36.18316
2009	33.50668
2010	31.85222
2011	27.84769
2012	33.77462
2013	29.60764
2014	32.62427
2015	31.55645
2016	22.97758
2017	21.23054
2018	21.99347
2019	20.16402
2020	20.32086
2021	6.35709
2022	5.03129