Year	Percent
1970	0.41845
1971	0.31672
1972	0.3227
1973	0.42562
1974	0.64669
1975	0.4334
1976	0.26252
1977	0.46216
1978	0.48775
1979	0.42158
1980	0.46811
1981	0.40121
1982	0.27105
1983	0.30823
1984	0.45187
1985	0.46923
1986	0.42203
1987	0.55019
1988	0.83329
1989	1.00505
1990	1.03872
1991	1.19381
1992	1.55833
1993	1.56893
1994	1.13324
1995	1.4825
1996	1.36839
1997	1.58636
1998	1.96383
1999	3.08089
2000	3.03779
2001	3.64169
2002	3.44601
2003	2.29967
2004	1.68174
2005	3.87861
2006	3.4049
2007	3.15296
2008	2.33003
2009	0.68322
2010	1.47203
2011	1.54441
2012	1.22774
2013	1.12374
2014	0.20369
2015	1.75552
2016	1.83964
2017	1.83294