Year	Percent
1960	4.90536
1961	4.46848
1962	4.09016
1963	3.91806
1964	4.04323
1965	4.35321
1966	4.67666
1967	4.88316
1968	6.90644
1969	8.0623
1970	7.71394
1971	3.65394
1972	3.56714
1973	3.40366
1974	3.16629
1975	2.8847
1976	1.77638
1977	1.52071
1978	1.36822
1979	1.35315
1980	1.433
1981	1.7335
1982	1.81283
1983	1.85403
1984	1.84227
1985	1.79138
1986	1.72648
1987	1.68206
1988	1.66717
1989	1.69235
1990	1.73969
1991	1.79711
1992	1.83274
1993	1.80666
1994	1.64907
1995	1.44297
1996	1.27644
1997	1.1329
1998	1.03239
1999	0.9932
2000	0.99465
2001	1.01318
2002	1.01448
2003	0.99212
2004	0.94034
2005	0.8639
2006	0.78636
2007	0.71939
2008	0.67331
2009	0.78192
2010	0.82612
2011	0.82775
2012	0.82989
2013	0.82538
2014	0.81552
2015	0.79911
2016	0.80887
2017	0.81729