Year	Percent
1975	0.57534
1976	0.4658
1977	0.53631
1978	0.23182
1979	0.20196
1980	0.58683
1981	0.83382
1982	0.52164
1983	0.87308
1984	0.95943
1985	0.41953
1986	0.6091
1987	0.69641
1988	1.79248
1989	2.45734
1990	2.86321
1991	2.05018
1992	1.89589
1993	1.39968
1994	0.93156
1995	1.22162
1996	1.27617
1997	2.59339
1998	6.4348
1999	4.81782
2000	2.66313
2001	4.21223
2002	2.48815
2003	3.43594
2004	3.38948
2005	4.33958
2006	4.02125
2007	3.28357
2008	2.93825
2009	2.27591
2010	4.32321
2011	0.66709
2012	3.24457
2013	3.79127
2014	1.22145
2015	2.22411
2016	0.74395
2017	1.74511