Year	Percent
1960	5.31923
1961	5.23021
1962	5.20097
1963	5.16856
1964	5.12404
1965	5.08949
1966	5.0488
1967	4.99738
1968	4.92756
1969	4.82368
1970	4.70979
1971	2.97773
1972	2.88317
1973	2.80807
1974	2.76326
1975	2.73306
1976	2.70989
1977	2.68534
1978	2.68349
1979	2.7127
1980	2.61185
1981	2.60394
1982	2.64298
1983	2.66065
1984	2.65681
1985	2.63629
1986	2.61029
1987	2.57124
1988	2.54208
1989	2.88758
1990	3.97533
1991	3.93948
1992	3.8843
1993	3.78794
1994	3.65658
1995	3.49284
1996	3.32398
1997	3.171
1998	3.03474
1999	3.0795
2000	3.43174
2001	3.34209
2002	3.27706
2003	3.21262
2004	3.17802
2005	3.14725
2006	3.1283
2007	3.11468
2008	3.11367
2009	3.13747
2010	3.20752
2011	3.24014
2012	3.26787
2013	3.25935
2014	3.23133
2015	3.17731
2016	3.1126
2017	3.03891