Year	Percent
1960	4.96963
1961	4.8997
1962	4.80912
1963	4.87003
1964	5.10353
1965	4.98857
1966	5.0184
1967	5.04816
1968	5.08223
1969	5.08873
1970	5.54985
1971	5.39182
1972	5.52412
1973	6.669
1974	8.17723
1975	8.21275
1976	7.96315
1977	7.6392
1978	7.93038
1979	8.74303
1980	9.80865
1981	9.50617
1982	8.46666
1983	7.61368
1984	7.48344
1985	6.97556
1986	6.99323
1987	7.47285
1988	8.46435
1989	8.91337
1990	9.2293
1991	9.63602
1992	9.68075
1993	9.51922
1994	9.86405
1995	10.60551
1996	10.71072
1997	11.0798
1998	10.4848
1999	10.26828
2000	10.66464
2001	9.66607
2002	9.13239
2003	9.03752
2004	9.62537
2005	9.9964
2006	10.65479
2007	11.49791
2008	12.5144
2009	11.01166
2010	12.3783
2011	13.57379
2012	13.60661
2013	13.63931
2014	13.62004
2015	12.49904
2016	11.89062