Year	Percent
1960	2.90725
1961	2.96724
1962	2.85932
1963	2.78482
1964	2.61539
1965	2.54215
1966	2.51439
1967	2.33501
1968	2.32035
1969	2.26343
1970	2.18417
1971	1.97132
1972	1.876
1973	1.76829
1974	1.71271
1975	1.682
1976	1.59656
1977	1.55904
1978	1.5192
1979	1.51687
1980	1.55846
1981	1.5602
1982	1.54547
1983	1.47422
1984	1.23402
1985	0.98457
1986	0.99472
1987	0.98513
1988	0.97919
1989	0.98909
1990	0.98513
1991	0.98979
1992	1.03916
1993	1.01582
1994	1.00616
1995	1.0062
1996	0.95278
1997	0.93771
1998	0.72187
1999	0.71079
2000	0.83618
2001	0.76724
2002	0.57796
2003	0.51832
2004	0.39633
2005	0.212
2006	0.5252
2007	0.50523
2008	0.75932
2009	0.51468
2010	0.49823
2011	0.76897
2012	0.52571
2013	0.45522
2014	0.62815
2015	0.52729
2016	0.45132
2017	0.42935