Year	Percent
1960	43.22296
1961	41.9259
1962	40.67605
1963	39.72679
1964	38.57225
1965	33.84146
1966	39.29539
1967	41.26089
1968	43.68421
1969	38.70387
1970	32.99492
1971	32.98458
1972	33.00551
1973	33.0776
1974	31.78649
1975	27.54616
1976	24.6677
1977	22.60355
1978	18.43747
1979	14.47172
1980	12.7039
1981	12.37062
1982	10.27224
1983	7.97138
1984	6.89302
1985	5.92187
1986	5.28679
1987	6.24489
1988	5.63195
1989	4.69699
1990	4.52615
1991	4.3769
1992	4.63279
1993	4.52119
1994	3.75614
1995	4.63772
1996	3.69099
1997	3.54271
1998	3.16686
1999	2.99077
2000	2.7947
2001	2.59029
2002	2.42562
2003	2.72239
2004	2.25959
2005	1.82838
2006	1.73894
2007	1.92668
2008	2.14007
2009	2.37598
2010	2.09104
2011	2.11892
2012	2.31481
2013	1.99354
2014	1.8196
2015	1.94776
2016	1.97589
2017	1.84199
2018	2.11731
2019	2.08343
2020	2.20806
2021	1.78984
2022	1.75854