Year	Percent
1960	2.72888
1961	2.58681
1962	3.01827
1963	3.04152
1964	2.84291
1965	2.83214
1966	2.63675
1967	2.58821
1968	2.67593
1969	2.39161
1970	2.42912
1971	2.36222
1972	2.17997
1973	1.97581
1974	2.23484
1975	2.39725
1976	2.2042
1977	2.2163
1978	2.27182
1979	2.25153
1980	2.36309
1981	2.43867
1982	2.4199
1983	2.36474
1984	2.23547
1985	2.10467
1986	1.94482
1987	2.03165
1988	2.08747
1989	2.02422
1990	1.95076
1991	1.95468
1992	1.88938
1993	1.9072
1994	1.77011
1995	1.68531
1996	1.64482
1997	1.61596
1998	1.60803
1999	1.56485
2000	1.45744
2001	1.53238
2002	1.50815
2003	1.46685
2004	1.4237
2005	1.31149
2006	1.37749
2007	1.30725
2008	1.355
2009	1.35018
2010	1.39862
2011	1.31353
2012	1.35182
2013	1.22725
2014	1.15155
2015	1.11648
2016	1.17152
2017	1.17436