Year	Percent
1960	13.38965
1961	13.91103
1962	14.03038
1963	12.94828
1964	13.72762
1965	13.50026
1966	13.91262
1967	14.3619
1968	14.94101
1969	13.20679
1970	16.25984
1971	15.91238
1972	14.5651
1973	15.72878
1974	18.39108
1975	14.40267
1976	16.08393
1977	15.35404
1978	16.42274
1979	17.7786
1980	16.94491
1981	15.10046
1982	6.56197
1983	16.41888
1984	18.01781
1985	11.90664
1986	13.3941
1987	15.44925
1988	15.01914
1989	13.78142
1990	13.48021
1991	11.95163
1992	11.09075
1993	13.32345
1994	16.1056
1995	21.92902
1996	17.54351
1997	18.54384
1998	18.49163
1999	18.31812
2000	16.8901
2001	14.66579
2002	12.68994
2003	24.63297
2004	51.00886
2005	47.97727
2006	47.58444
2007	44.50349
2008	42.69451
2009	35.13835
2010	36.84561
2011	38.87726
2012	38.46805
2013	33.56559
2014	34.16136
2015	29.89306
2016	28.19169
2017	33.85392