Year	Percent
1960	3.90172
1961	2.74674
1962	2.67331
1963	2.72045
1964	2.76197
1965	2.68773
1966	3.26116
1967	3.15816
1968	3.06146
1969	4.42333
1970	7.4108
1971	6.89929
1972	4.4814
1973	2.36231
1974	1.92684
1975	1.13853
1976	1.12572
1977	1.48151
1978	1.0969
1979	0.72464
1980	1.11292
1981	1.83946
1982	2.11556
1983	2.03811
1984	1.96444
1985	1.82952
1986	1.86022
1987	1.98213
1988	1.94361
1989	1.96528
1990	2.36899
1991	2.57797
1992	2.49872
1993	2.57882
1994	2.66663
1995	2.26152
1996	1.91533
1997	1.93198
1998	1.89877
1999	1.89876
2000	1.90137
2001	1.90179
2002	1.89881
2003	1.70377
2004	1.52146
2005	1.51847
2006	1.49575
2007	1.47371
2008	1.45231
2009	1.30962
2010	1.53322
2011	1.82509
2012	1.81168
2013	1.77944
2014	1.65511
2015	1.6098
2016	1.51201
2017	1.40395