Year	Percent
1960	5.73952
1961	6.4215
1962	6.96039
1963	7.21179
1964	7.17763
1965	6.83247
1966	6.54789
1967	6.30052
1968	8.67629
1969	8.73758
1970	8.90967
1971	9.16371
1972	9.21347
1973	9.00893
1974	4.36423
1975	3.41084
1976	2.97961
1977	2.62547
1978	2.5583
1979	2.71452
1980	3.05315
1981	5.11783
1982	5.73805
1983	5.88319
1984	5.95493
1985	5.983
1986	5.99481
1987	5.94013
1988	5.61051
1989	4.65682
1990	3.7113
1991	2.97774
1992	2.35694
1993	1.85603
1994	1.55158
1995	1.3635
1996	1.24657
1997	1.05339
1998	0.93154
1999	0.79887
2000	0.92682
2001	0.8019
2002	0.69642
2003	0.65331
2004	0.64091
2005	0.66924
2006	0.73988
2007	0.79563
2008	0.82891
2009	0.85348
2010	0.84885
2011	0.8597
2012	0.84983
2013	0.84519
2014	0.78296
2015	0.74452
2016	0.68465
2017	0.64561