Year	Percent
1963	5.9027
1964	5.96631
1965	7.69009
1966	11.32423
1967	11.51183
1968	8.08745
1969	9.57052
1970	9.40353
1971	8.64019
1972	10.08155
1973	10.84045
1977	15.64882
1978	16.73657
1979	15.76881
1980	12.61336
1981	13.26524
1982	17.72025
1983	16.97293
1984	19.00435
1985	16.9952
1987	16.89641
1988	15.15188
1989	13.39032
1990	14.02429
1991	12.46981
1992	11.28416
1993	12.46537
1994	10.64478
1995	9.27847
1996	8.46808
1997	11.00094
1998	14.31104
1999	11.38194
2000	10.59439
2001	11.48921
2002	9.81265
2003	8.73711
2004	8.08156
2005	7.7306
2006	7.84837
2007	8.52705
2008	7.35344
2009	9.6172
2010	8.58837
2011	7.24876
2012	7.69772
2013	9.004
2014	10.71359
2015	13.49623
2016	9.90648
2017	10.28867