Year	Percent
1960	4.19658
1961	4.02982
1962	4.13155
1963	4.08707
1964	4.0974
1965	4.23558
1966	4.55215
1967	4.63038
1968	4.9443
1969	4.95147
1970	5.18271
1971	5.33855
1972	5.78705
1973	6.38123
1974	8.22979
1975	7.2667
1976	8.05001
1977	8.74627
1978	9.00677
1979	9.59959
1980	10.26475
1981	9.89609
1982	9.06379
1983	9.03314
1984	10.02568
1985	9.59865
1986	9.86605
1987	10.44541
1988	10.54697
1989	10.44652
1990	10.53131
1991	10.09949
1992	10.212
1993	10.46669
1994	11.12946
1995	11.77667
1996	11.90052
1997	12.26432
1998	12.27494
1999	12.92474
2000	14.31854
2001	13.13707
2002	13.01727
2003	13.41307
2004	14.66955
2005	15.50427
2006	16.21883
2007	16.46102
2008	17.42701
2009	13.75417
2010	15.80415
2011	17.31137
2012	17.10802
2013	16.58695
2014	16.54362
2015	15.39099
2016	14.6893