Year	Percent
1970	0.49762
1971	0.48196
1972	0.6042
1973	0.49476
1974	0.47839
1975	0.44626
1976	0.50387
1977	0.40237
1978	0.53411
1979	0.57124
1980	0.43954
1981	0.47234
1982	0.35255
1983	0.38337
1984	0.65433
1985	0.7531
1986	0.90162
1987	0.63878
1988	0.85678
1989	0.9569
1990	1.36189
1991	1.25124
1992	0.89929
1993	0.85281
1994	0.90012
1995	1.53647
1996	2.41916
1997	2.23235
1998	4.32432
1999	6.33743
2000	5.03447
2001	3.60039
2002	0.82785
2003	1.56856
2004	0.32204
2005	3.10975
2006	4.9273
2007	4.08929
2008	2.61141
2009	2.91555
2010	4.29294
2011	2.86957
2012	2.79661
2013	2.49029
2014	2.95769
2015	3.82024
2016	2.62295
2017	3.40018