Year	Percent
1970	0.1877
1971	0.21708
1972	0.24885
1973	0.21874
1974	0.24222
1975	0.3005
1976	0.39615
1977	0.50758
1978	0.8731
1979	0.93886
1980	0.86205
1981	0.91942
1982	1.25112
1983	1.34477
1984	1.32439
1985	1.2275
1986	1.13088
1987	2.1335
1988	2.22285
1989	2.45913
1990	2.2843
1991	2.34719
1992	1.99288
1993	1.95837
1994	1.84391
1995	1.77834
1996	1.54285
1997	1.47861
1998	1.36403
1999	1.22605
2000	1.90237
2001	1.97776
2002	1.67909
2003	1.61305
2004	1.71858
2005	1.4464
2006	1.75755
2007	2.23713
2008	1.52084
2009	1.7866
2010	1.60511
2011	1.61045
2012	1.48883
2013	1.38483
2014	1.01682
2015	0.96601
2016	0.96061
2017	0.90102