Year	Percent
1960	20.43378
1961	20.04998
1962	15.59871
1963	11.51321
1964	11.74233
1965	13.65244
1966	14.9489
1967	17.42558
1968	21.12328
1969	16.89154
1970	18.33778
1971	20.17109
1972	23.70471
1973	22.87554
1974	24.74395
1975	23.63248
1976	16.11087
1977	17.1857
1978	10.69518
1979	11.40963
1980	16.93698
1981	20.8159
1982	19.05374
1983	14.30516
1984	17.0355
1985	17.81998
1986	18.05636
1987	14.93616
1988	18.70172
1989	15.03798
1990	17.37694
1991	19.1034
1992	20.23726
1993	22.77489
1994	23.72906
1995	19.66019
1996	18.54194
1997	18.1339
1998	20.75046
1999	14.39628
2000	13.56942
2001	10.26647
2002	5
2003	8
2004	4.50911
2005	1.52518
2006	1.57116
2007	7.10975
2008	5.12791
2009	14.29066
2010	22.27808
2011	20.27879
2012	11.84489
2013	11.37853
2014	11.82563
2015	12.28744
2016	12.19246
2017	16.86269