Year	Percent
1960	5.44605
1961	5.45112
1962	5.47272
1963	5.50002
1964	5.51584
1965	5.52149
1966	5.48573
1967	5.11705
1968	5.15286
1969	5.16157
1970	5.19384
1971	5.69968
1972	5.72577
1973	5.72596
1974	5.73317
1975	5.71003
1976	5.38164
1977	5.37807
1978	5.37695
1979	5.36734
1980	5.36569
1981	5.35519
1982	5.3476
1983	5.33018
1984	5.3008
1985	5.26126
1986	5.2302
1987	5.19828
1988	5.19696
1989	5.19367
1990	5.22601
1991	5.2438
1992	5.26114
1993	5.27918
1994	4.16106
1995	4.09411
1996	4.13217
1997	4.15607
1998	4.16381
1999	4.14815
2000	4.11279
2001	4.07649
2002	4.04161
2003	4.00202
2004	3.96624
2005	5.06886
2006	5.01948
2007	4.96672
2008	4.92115
2009	4.86004
2010	4.80729
2011	4.75202
2012	4.70016
2013	4.65335
2014	4.61895
2015	4.58487
2016	4.55524
2017	4.52097