Year	Percent
1960	5.69789
1961	5.7057
1962	5.74636
1963	5.76046
1964	5.76592
1965	5.76683
1966	5.76045
1967	5.7722
1968	9.57244
1969	10.25995
1970	10.26666
1971	10.29958
1972	10.29087
1973	10.24477
1974	10.18718
1975	10.09689
1976	10.01602
1977	9.89883
1978	9.81798
1979	6.57707
1980	6.00208
1981	5.98101
1982	5.98795
1983	5.96132
1984	5.93671
1985	5.87914
1986	5.82865
1987	5.77601
1988	5.78046
1989	4.96143
1990	4.89242
1991	5.00584
1992	5.07304
1993	5.03866
1994	4.89754
1995	4.68504
1996	4.4665
1997	4.29426
1998	4.19666
1999	4.19502
2000	4.26398
2001	4.33313
2002	4.39543
2003	5.27923
2004	5.47943
2005	5.52442
2006	5.57539
2007	5.61475
2008	5.63776
2009	5.61694
2010	5.59118
2011	5.54771
2012	5.51384
2013	5.47184
2014	5.42519
2015	5.38176
2016	5.3318
2017	5.28163