Year	Percent
1960	23.28675
1961	23.68081
1962	22.54463
1963	23.29378
1964	23.7278
1965	24.98597
1966	25.54106
1967	23.38996
1968	25.46277
1969	23.07163
1970	23.71914
1971	20.6498
1972	24.26832
1973	22.26365
1974	23.48955
1975	29.77939
1976	29.75666
1977	26.99631
1978	20.79958
1979	23.62593
1980	18.51958
1981	20.66362
1982	21.19901
1983	17.02754
1984	18.42826
1985	21.32741
1986	22.02123
1987	22.62281
1988	19.28707
1989	21.17535
1990	18.46614
1991	18.69641
1992	17.14343
1993	19.16536
1994	17.74001
1995	19.47016
1996	18.33706
1997	18.1914
1998	17.83193
1999	17.37601
2000	16.43925
2001	16.25243
2002	13.38078
2003	15.4911
2004	14.2018
2005	15.1804
2006	13.39515
2007	12.24591
2008	14.68663
2009	16.10773
2010	15.94526
2011	12.94706
2012	14.09769
2013	13.72488
2014	13.36877
2015	14.27263
2016	14.41402
2017	14.98203
2018	14.98752
2019	14.89627
2020	16.14878
2021	15.46872
2022	15.48853