Year	Percent
1960	32.1042
1961	32.90995
1962	31.09252
1963	32.34974
1964	30.96239
1965	28.56489
1966	28.68265
1967	30.07723
1968	31.62787
1969	29.32324
1970	28.76777
1971	27.52396
1972	26.7387
1973	27.66916
1974	33.52872
1975	30.64943
1976	29.32061
1977	30.97782
1978	30.78519
1979	27.2363
1980	27.81799
1981	27.96159
1982	26.59945
1983	28.47601
1984	28.85649
1985	28.05746
1986	27.455
1987	27.30229
1988	26.68362
1989	25.95598
1990	26.685
1991	27.08797
1992	26.12236
1993	24.8807
1994	23.97384
1995	23.14012
1996	22.53906
1997	21.9486
1998	21.16449
1999	20.72848
2000	19.92732
2001	20.06661
2002	14.27932
2003	13.23051
2004	12.5438
2005	11.81948
2006	11.33628
2007	11.68316
2008	13.3792
2009	12.69197
2010	9.04834
2011	9.53316
2012	7.91029
2013	7.9246
2014	8.08071
2015	8.21694
2016	7.26172
2017	7.43068
2018	7.59207
2019	7.25625
2020	8.23801
2021	8.83463
2022	8.74925