Year	Percent
1960	5.23153
1961	5.22979
1962	4.31965
1963	3.86521
1964	3.7835
1965	4.21207
1966	3.46272
1967	3.19187
1968	3.24517
1969	2.64782
1970	2.41669
1971	2.19622
1972	1.98752
1973	1.79127
1974	1.96507
1975	1.83101
1976	1.92838
1977	1.88572
1978	2.17557
1979	2.18229
1980	1.58354
1981	1.72013
1982	1.58204
1983	1.36651
1984	1.1989
1985	1.21005
1986	1.34415
1987	1.01814
1988	0.88005
1989	0.80037
1990	0.67573
1991	0.34816
1992	0.55909
1993	0.75507
1994	0.73377
1995	0.54948
1996	0.63365
1997	0.79693
1998	0.78006
1999	0.81624
2000	1.0301
2001	1.2135
2002	1.05892
2003	0.76415
2004	0.68762
2005	0.76654
2006	0.68342
2007	0.62762
2008	0.69986
2009	0.66746
2010	0.66788
2011	0.6036
2012	0.65363
2013	0.6187
2014	0.6708
2015	0.67253
2016	0.67033
2017	0.66191