Year	Percent
1960	39.72092
1961	38.73725
1962	38.47387
1963	38.02655
1964	36.59091
1965	35.84336
1966	36.55656
1967	39.90414
1968	39.52595
1969	38.38861
1970	37.10214
1971	37.21627
1972	37.8145
1973	36.47669
1974	36.7001
1975	36.95937
1976	35.77671
1977	35.49884
1978	36.09208
1979	41.26618
1980	45.7324
1981	40.27126
1982	39.9724
1983	38.88458
1984	32.57152
1985	37.04538
1986	31.67456
1987	31.77957
1988	35.19042
1989	30.1661
1990	27.88865
1991	35.50783
1992	34.32437
1993	31.37197
1994	37.21829
1995	35.05874
1996	37.54797
1997	38.34468
1998	39.00492
1999	38.0688
2000	40.70514
2001	40.29544
2002	37.90293
2003	25.63394
2004	29.77426
2005	23.78095
2006	26.69613
2007	26.53735
2008	24.85729
2009	26.99871
2010	27.71343
2011	22.80833
2012	24.58077
2013	22.91557
2014	25.46778
2015	30.46301
2016	26.97086
2017	32.81222
2018	27.99699
2019	24.13539
2020	27.06408
2021	25.30361
2022	22.5951