Year	Percent
1974	2.88087
1975	4.71803
1976	4.51565
1977	3.94429
1978	13.39802
1979	14.01824
1980	21.92745
1981	31.89426
1982	55.61668
1983	37.13525
1984	27.0446
1985	33.96251
1986	30.56338
1987	29.50174
1988	34.93801
1989	27.75411
1990	17.84248
1991	25.44454
1992	12.51916
1993	25.19084
1994	24.2497
1995	17.06073
1996	14.69658
1997	20.19527
1998	16.22364
1999	9.5378
2000	7.95983
2001	8.28289
2002	7.6172
2003	8.71737
2004	7.79124
2005	6.75789
2006	26.65357
2007	3.97758
2008	2.43519
2009	3.2431
2010	1.75694
2011	2.43442
2012	2.19834
2013	2.68363
2014	3.37515
2015	6.34175