Year	Percent
1960	7.15755
1961	6.72615
1962	6.8672
1963	4.82386
1964	4.13444
1965	4.41047
1966	4.68887
1967	4.68514
1968	4.73064
1969	4.69439
1970	4.40335
1971	4.73499
1972	5.01007
1973	4.03473
1974	4.54145
1975	4.87872
1976	5.90816
1977	6.03494
1978	6.37145
1979	5.52588
1980	6.39877
1981	6.41586
1982	6.24089
1983	5.72681
1984	5.25454
1985	5.22553
1986	4.94826
1987	4.46861
1988	4.28122
1989	4.29024
1990	4.0023
1991	3.71113
1992	3.69027
1993	3.41789
1994	3.19275
1995	2.89233
1996	2.74348
1997	2.66339
1998	2.79444
1999	2.49258
2000	2.45732
2001	2.42788
2002	2.31547
2003	2.32866
2004	2.33106
2005	2.46728
2006	2.48837
2007	2.46964
2008	2.60148
2009	2.72477
2010	2.57425
2011	2.57735
2012	2.61298
2013	2.61462
2014	2.66077
2015	2.64476
2016	2.61832
2017	2.5549