Year	Percent
1960	5.55249
1961	5.63753
1962	5.71081
1963	5.74575
1964	5.77954
1965	5.77844
1966	5.75891
1967	5.72721
1968	4.4544
1969	4.5361
1970	4.66625
1971	4.81689
1972	4.93447
1973	4.84917
1974	4.55536
1975	4.15215
1976	3.69185
1977	3.33463
1978	3.23197
1979	3.43798
1980	3.83244
1981	4.29968
1982	4.67069
1983	4.94343
1984	5.07505
1985	5.13987
1986	5.13902
1987	5.15686
1988	5.20037
1989	5.27459
1990	5.37133
1991	5.47403
1992	5.51756
1993	5.5031
1994	5.38835
1995	4.79019
1996	4.45532
1997	4.30938
1998	4.21918
1999	4.16963
2000	4.16967
2001	4.15642
2002	4.15666
2003	4.12564
2004	4.08504
2005	4.03498
2006	3.98968
2007	4.04545
2008	5.07652
2009	5.04095
2010	5.03149
2011	5.01126
2012	4.99573
2013	4.86845
2014	4.83078
2015	4.77963
2016	4.73126
2017	4.67407