Year	Percent
1960	2.52896
1961	2.27915
1962	2.29739
1963	2.39885
1964	2.40377
1965	2.63309
1966	2.91685
1967	3.03156
1968	3.21105
1969	3.16149
1970	3.31587
1971	3.22523
1972	3.84646
1973	3.41744
1974	2.56457
1975	3.125
1976	2.98996
1977	2.88864
1978	2.95853
1979	2.0264
1980	2.18145
1981	2.52786
1982	3.8033
1983	3.64524
1984	3.50819
1985	3.75763
1986	3.80407
1987	2.77319
1988	3.19547
1989	2.42576
1990	2.13188
1991	2.82933
1992	2.36889
1993	2.17855
1994	2.04677
1995	2.28342
1996	2.06379
1997	1.68568
1998	1.54315
1999	1.38877
2000	1.34515
2001	1.19149
2002	1.105
2003	0.96404
2004	1.05139
2005	0.88692
2006	1.00089
2007	0.95972
2008	0.90878
2009	1.05742
2010	1.0206
2011	1.1359
2012	1.30476
2013	1.28156
2014	1.29001
2015	1.4168
2016	1.26337
2017	1.18416