Year	Percent
1960	43.1892
1961	41.72743
1962	40.02923
1963	38.84001
1964	38.32405
1965	36.9683
1966	33.8369
1967	35.05317
1968	36.54168
1969	33.95004
1970	33.43176
1971	31.96629
1972	32.8023
1973	32.45866
1974	31.87669
1975	30.16019
1976	29.40843
1977	29.36133
1978	28.67683
1979	27.7798
1980	26.54551
1981	27.46229
1982	28.44777
1983	27.2732
1984	24.9046
1985	25.68912
1986	25.03265
1987	23.63545
1988	23.15332
1989	23.91363
1990	23.06707
1991	22.84245
1992	23.31001
1993	22.19794
1994	22.75282
1995	23.42188
1996	23.1958
1997	24.48425
1998	25.30314
1999	25.16929
2000	25.38714
2001	24.14496
2002	22.70263
2003	22.15194
2004	22.00189
2005	21.57451
2006	20.41835
2007	19.93795
2008	20.35137
2009	21.78692
2010	22.68881
2011	23.81964
2012	23.3862
2013	23.70759
2014	23.49273
2015	23.26284
2016	22.32833
2017	21.9632
2018	21.65124
2019	20.67787
2020	21.85413
2021	22.66251
2022	22.35191