Year	Percent
1960	1.55
1961	2.14
1962	2.66
1963	1.68
1964	1.15
1965	1.07
1966	1.168
1967	1.4
1968	1.68571
1969	1.9375
1970	1.87778
1971	1.80769
1972	1.82381
1973	1.84857
1974	1.65918
1975	2.04196
1976	3.78129
1977	4.0086
1978	4.71914
1979	4.67336
1980	3.09896
1981	3.46535
1982	2.70456
1983	2.73881
1984	2.16204
1985	2.29972
1986	2.31368
1987	2.28439
1988	2.12494
1989	1.88037
1990	1.45091
1991	1.50693
1992	1.42122
1993	1.4228
1994	1.45704
1995	1.47307
1996	1.24123
1997	1.14014
1998	1.13632
1999	1.22036
2000	1.14882
2001	1.18423
2002	1.09188
2003	1.0609
2004	0.8833
2005	0.84715
2006	0.78823
2007	0.79255
2008	0.76276
2009	0.88651
2010	0.81488
2011	0.76429
2012	0.78482
2013	0.83774
2014	0.8781
2015	0.86472
2016	0.82713
2017	0.90966