Year	Percent
1970	0.02729
1971	0.76249
1972	0.20287
1973	0.68789
1974	0.71322
1975	0.5246
1976	0.87926
1977	0.64219
1978	0.53671
1979	1.21348
1980	1.41124
1981	1.36497
1982	1.46765
1983	0.73775
1984	0.94902
1985	0.85205
1986	0.90467
1987	0.81549
1988	0.87861
1989	0.64484
1990	0.29654
1991	0.23948
1992	0.10781
1993	0.2968
1994	0.00013
1995	0.17102
1996	0.16047
1997	0.14034
1998	0.35636
1999	0.09494
2000	0.4795
2001	0.27672
2002	0.15558
2003	0.25458
2004	0.3686
2005	0.40677
2006	0.97211
2007	2.15131
2008	2.12642
2009	2.2062
2010	4.33918
2011	1.81471
2012	3.47602
2013	3.38028
2014	3.92614
2015	2.69806
2016	3.14193
2017	3.21137