Year	Percent
1960	10.77442
1961	8.06452
1962	10.18519
1963	12.82052
1964	20.14743
1965	22.44009
1966	16.38417
1967	12.63158
1968	11.01836
1969	13.21841
1970	15.09973
1971	18.88467
1972	20.68557
1973	21.74393
1974	16.38251
1975	27.6644
1976	24.86487
1977	34.34555
1978	52.68816
1979	48.81382
1980	28.44647
1981	23.82409
1982	21.33333
1983	20.5963
1984	15.04143
1985	16.63358
1986	18.82961
1987	17.63985
1988	16.02726
1989	16.51984
1990	26.57097
1991	17.11375
1992	15.71139
1993	7.47795
1994	15.04351
1995	16.12978
1996	18.76867
1997	16.28748
1998	16.43731
1999	13.33986
2000	15.18
2001	15.61293
2002	16.11918
2003	14.42836
2004	14.51455
2005	16.29202
2006	16.77496
2007	14.64252
2008	17.32138
2009	17.98491
2010	18.93082
2011	18.25917
2012	24.19221
2013	24.56016
2014	23.14254
2015	20.73526
2016	22.87599
2017	26.41394