Year	Percent
1960	47.90792
1961	46.40683
1962	45.90405
1963	44.1671
1964	39.80136
1965	39.61846
1966	37.44038
1967	34.75976
1968	35.56116
1969	33.5688
1970	31.86677
1971	30.88033
1972	29.80047
1973	31.0499
1974	25.46685
1975	28.24446
1976	24.47935
1977	24.26585
1978	25.88064
1979	26.40239
1980	25.88027
1981	26.534
1982	24.12531
1983	21.88196
1984	24.13447
1985	26.53758
1986	28.46154
1987	29.18235
1988	32.03932
1989	32.71644
1990	32.49843
1991	33.29394
1992	34.00969
1993	28.21521
1994	25.26363
1995	24.72761
1996	16.52673
1997	15.1463
1998	15.54162
1999	15.21777
2000	16.19515
2001	17.2771
2002	18.73731
2003	20.77602
2004	16.64002
2005	16.06519
2006	15.94479
2007	15.57875
2008	16.18548
2009	15.24958
2010	17.48892
2011	18.48667
2012	16.37515
2013	15.3429
2014	15.24176
2015	18.36204
2016	17.86365
2017	17.31433
2018	18.22627
2019	17.49709
2020	19.09412
2021	17.46652
2022	16.71537