Year	Percent
1970	0.60322
1971	0.48126
1972	0.57156
1973	0.65381
1974	0.33316
1975	0.81294
1976	0.6029
1977	0.54076
1978	0.60978
1979	0.93916
1980	0.66515
1981	0.31486
1982	0.23241
1983	0.24106
1984	0.31727
1985	0.08466
1986	0.42535
1987	0.81715
1988	0.41315
1989	0.90107
1990	1.00241
1991	0.79802
1992	0.89872
1993	1.20371
1994	1.23126
1995	1.43605
1996	1.27182
1997	1.41
1998	1.92273
1999	2.56179
2000	1.8121
2001	1.37491
2002	1.63047
2003	1.69597
2004	3.04689
2005	0.40165
2006	2.04823
2007	3.61862
2008	2.33435
2009	2.16799
2010	2.33774
2011	2.81362
2012	2.33509
2013	2.35327
2014	2.22365
2015	1.6945
2016	1.68045
2017	1.95569