Year	Percent
1960	5.25829
1961	5.33309
1962	5.36359
1963	5.27536
1964	5.06788
1965	4.76915
1966	4.46537
1967	3.67368
1968	3.35848
1969	3.25904
1970	3.22971
1971	3.21808
1972	3.19345
1973	3.15642
1974	3.1061
1975	3.04936
1976	2.95545
1977	2.34838
1978	2.23713
1979	2.38082
1980	2.58086
1981	2.83811
1982	3.01169
1983	2.93623
1984	2.5556
1985	1.99271
1986	1.35678
1987	2.11319
1988	2.07394
1989	2.11428
1990	2.40881
1991	2.7688
1992	3.0362
1993	3.18426
1994	3.15933
1995	3.01185
1996	2.86376
1997	2.03063
1998	1.76905
1999	1.59774
2000	1.40833
2001	1.18327
2002	0.98907
2003	0.91878
2004	1.01049
2005	1.21141
2006	1.46344
2007	1.66937
2008	1.97706
2009	2.01374
2010	1.92095
2011	1.80291
2012	1.71698
2013	1.65223
2014	1.63516
2015	1.64962
2016	1.66415
2017	1.66109