Year	Percent
1960	6.93173
1961	7.14056
1962	3.96423
1963	18.05168
1964	18.50968
1965	16.86321
1966	8.32657
1967	12.01961
1968	11.24759
1969	12.8268
1970	14.92226
1971	18.39278
1972	18.64687
1973	16.72023
1974	17.09392
1975	17.82065
1976	14.47071
1977	21.39363
1978	11.93044
1979	12.7398
1980	9.95657
1981	10.50102
1982	8.31931
1983	9.32472
1984	10.49216
1985	12.50219
1986	13.19887
1987	14.16338
1988	14.42866
1989	14.30274
1990	9.05004
1991	0
1992	6.77966
1993	1.74591
1994	7.90003
1995	9.3736
1996	27.85182
1997	2.5
1998	2.1
1999	3.06901
2000	14.4335
2001	6.70414
2002	7.43579
2003	9.52455
2004	12.25692
2005	11.7799
2006	14.64634
2007	13.70828
2008	10.8571
2009	14.56344
2010	28.78135
2011	24.89211
2012	14.32823
2013	21.84242
2014	23.22347
2015	19.56563
2016	17.39994
2017	20.7945