Year	Percent
1960	25.9006
1961	24.90257
1962	23.8275
1963	22.25722
1964	20.76607
1965	18.59562
1966	17.44182
1967	16.51589
1968	15.85361
1969	14.4974
1970	12.99091
1971	12.7127
1972	11.9544
1973	9.86878
1974	6.93282
1975	6.67228
1976	6.48705
1977	5.66537
1978	7.46228
1979	8.57192
1980	11.06046
1981	13.69415
1982	12.77418
1983	11.05713
1984	12.30789
1985	12.77052
1986	15.22803
1987	16.30278
1988	15.38501
1989	15.57682
1990	12.49086
1991	12.01424
1992	12.05433
1993	10.39837
1994	10.55156
1995	12.61024
1996	10.34648
1997	9.8127
1998	11.55506
1999	9.91499
2000	9.06842
2001	8.31084
2002	7.82555
2003	7.45109
2004	6.88958
2005	6.50138
2006	7.11821
2007	7.18557
2008	6.12277
2009	6.92449
2010	6.49939
2011	4.64212
2012	6.79694
2013	8.77491
2014	9.37842
2015	10.0916
2016	9.78442
2017	9.82706
2018	11.13339
2019	13.32487
2020	12.213
2021	12.3931
2022	12.76532