Year	Percent
1960	41.74134
1961	41.09248
1962	39.06597
1963	39.82535
1964	41.34372
1965	39.3847
1966	40.35165
1967	42.75156
1968	42.08603
1969	41.58492
1970	40.28961
1971	38.63339
1972	38.62683
1973	41.60382
1974	38.87806
1975	35.99691
1976	34.31204
1977	35.77714
1978	34.27396
1979	32.82553
1980	34.40887
1981	33.2977
1982	32.32675
1983	32.60653
1984	31.38053
1985	29.71814
1986	28.64115
1987	27.97238
1988	28.76982
1989	27.83961
1990	27.58489
1991	27.66271
1992	26.89692
1993	27.05456
1994	26.51994
1995	24.45755
1996	25.19931
1997	24.24867
1998	24.18045
1999	22.97256
2000	21.61106
2001	21.61888
2002	19.53454
2003	19.592
2004	17.81469
2005	17.62021
2006	16.80944
2007	16.75012
2008	16.79094
2009	16.74427
2010	17.02651
2011	17.19197
2012	16.84538
2013	17.14842
2014	16.79193
2015	16.17451
2016	16.3638
2017	16.55833
2018	16.03163
2019	16.75557
2020	18.63553
2021	17.32626
2022	16.73084