Year	Percent
1960	33.81499
1961	35.26109
1962	35.39652
1963	34.41004
1964	34.48578
1965	36.4396
1966	36.16692
1967	35.37034
1968	34.63203
1969	32.72455
1970	29.32227
1971	28.24897
1972	28.01993
1973	28
1974	26.58289
1975	24.64413
1976	25.51929
1977	26.89428
1978	39.38804
1979	36.24858
1980	34.9606
1981	32.93801
1982	29.78047
1983	28.29657
1984	25.71563
1985	24.83814
1986	24.68967
1987	23.61302
1988	25.2099
1989	24.56612
1990	24.19137
1991	23.95994
1992	22.68459
1993	21.28719
1994	21.11651
1995	20.54077
1996	20.25457
1997	18.91812
1998	18.31396
1999	13.61819
2000	14.37252
2001	13.16599
2002	12.18341
2003	11.6141
2004	12.1707
2005	12.47092
2006	11.85658
2007	11.91105
2008	12.15017
2009	10.82504
2010	11.59122
2011	14.21966
2012	13.56629
2013	12.19113
2014	12.53835
2015	12.21598
2016	12.0499
2017	12.66977
2018	11.61016
2019	10.75365
2020	12.11718
2021	11.04085
2022	12.57249