Year	Percent
1970	1.67897
1971	1.71074
1972	1.39711
1973	1.57774
1974	1.28076
1975	1.2452
1976	0.53918
1977	0.48271
1978	0.70328
1979	0.96696
1980	1.18258
1981	1.11026
1982	0.78456
1983	0.89644
1984	1.20847
1985	1.05952
1986	1.57796
1987	1.25209
1988	1.84917
1989	3.35607
1990	3.39699
1991	1.73939
1992	1.72648
1993	1.82797
1994	1.904
1995	2.73357
1996	3.72542
1997	2.67671
1998	8.69849
1999	9.31449
2000	15.29014
2001	12.18538
2002	5.47032
2003	3.57441
2004	21.49292
2005	30.94629
2006	51.62546
2007	87.44259
2008	20.84878
2009	11.18168
2010	13.83683
2011	37.12848
2012	28.92284
2013	37.92446
2014	13.36746
2015	23.85274
2016	20.80048
2017	38.31292