Year	Percent
1960	3.77697
1961	3.72061
1962	3.86344
1963	3.96728
1964	3.8662
1965	3.91263
1966	3.85801
1967	3.61145
1968	3.47655
1969	3.45928
1970	3.35867
1971	3.41004
1972	3.40796
1973	3.27859
1974	3.2154
1975	3.0816
1976	3.00311
1977	3.10108
1978	3.14778
1979	3.12336
1980	2.92345
1981	2.94824
1982	2.85375
1983	2.73782
1984	2.67196
1985	2.67301
1986	2.58657
1987	2.65329
1988	2.58529
1989	2.50883
1990	2.56898
1991	2.45431
1992	2.44419
1993	2.38683
1994	2.27994
1995	2.16993
1996	2.15318
1997	1.96735
1998	1.92363
1999	1.90097
2000	1.8435
2001	1.72061
2002	1.64992
2003	1.60239
2004	1.44475
2005	1.41847
2006	1.32781
2007	1.30914
2008	1.17222
2009	1.17838
2010	1.2052
2011	1.12318
2012	1.14799
2013	1.12809
2014	1.14244
2015	1.08189
2016	1.05543
2017	1.02525