Year	Percent
1962	6.67548
1963	8.66469
1964	10.32839
1965	10.11743
1966	8.71827
1967	8.9077
1968	11.13304
1969	14.33605
1970	15.98788
1971	17.18701
1972	13.56453
1973	13.51351
1974	17.27424
1975	15.43185
1976	13.7269
1977	13.11206
1978	9.94071
1979	6.46894
1980	6.16031
1981	7.41691
1982	7.18896
1983	7.95867
1984	8.26523
1985	7.85693
1986	7.49813
1987	6.52874
1988	5.06088
1989	3.9681
1990	3.6462
1991	3.75378
1992	3.38102
1993	3.2527
1994	3.31629
1995	3.24069
1996	3.12794
1997	2.99824
1998	2.79628
1999	2.70205
2000	2.68259
2001	3.13925
2002	3.44722
2003	3.34084
2004	3.02565
2005	2.85394
2006	2.74038
2007	2.50246
2008	2.29304
2009	2.13728
2010	2.05343
2011	1.93159
2012	1.78966
2013	1.58728
2014	1.47267
2015	1.55492
2016	1.50451
2017	1.28592