Year	Percent
1960	31.53076
1961	30.26073
1962	34.75006
1963	38.79588
1964	36.84178
1965	33.06773
1966	35.70128
1967	27.52809
1968	23.15789
1969	29.08367
1970	30.08739
1971	33.5041
1972	35.90426
1973	29.87013
1974	27.72829
1975	24.85929
1976	25.7384
1977	26.09682
1978	31.3977
1979	28.53848
1980	19.51716
1981	19.28529
1982	16.41254
1983	13.93244
1984	17.7793
1985	16.94704
1986	18.97106
1987	14.17641
1988	13.81173
1989	13.04847
1990	8.87149
1991	9.83193
1992	7.71966
1993	8.87001
1994	11.42108
1995	10.07948
1996	11.98419
1997	10.87054
1998	11.02436
1999	11.11877
2000	12.31598
2001	12.09922
2002	12.50254
2003	12.38526
2004	9.65947
2005	10.97176
2006	11.18422
2007	10.75418
2008	9.99945
2009	9.25039
2010	10.15621
2011	9.71988
2012	10.20334
2013	10.11581
2014	9.23425
2015	9.35431
2016	8.95986
2017	8.42776
2018	8.51876
2019	8.5978
2020	8.11844
2021	8.10037
2022	8.58612