Year	Percent
1960	25.47521
1961	27.69231
1962	31.82927
1963	25.96154
1964	23.5
1965	19.37086
1966	13.92857
1967	11.4741
1968	13.54369
1969	14.76341
1970	11.43585
1971	13.16142
1972	17.92479
1973	18.17308
1974	21.9433
1975	23.95775
1976	21.6
1977	21.46727
1978	21.69697
1979	24.31083
1980	41.49135
1981	45.41812
2001	71.65879
2002	61.80942
2003	48.9785
2004	46.95897
2005	45.49333
2006	44.77713
2007	35.31141
2008	34.93367
2009	29.95029
2010	34.77947
2011	38.43145
2012	46.24879
2013	44.75559
2014	40.10317
2015	43.16434
2016	36.62534
2017	40.73926