Year	Percent
1974	29.8773
1975	16.58651
1976	3.28972
1977	37.75263
1978	4.80226
1979	7.86302
1980	19.35828
1981	27.62442
1982	28.73346
1983	23.03969
1984	31.00367
1985	42.28294
1986	52.26054
1987	56.78546
1988	52.51662
1989	50.23451
1990	45.88057
1991	32.94784
1992	19.03065
1993	14.8905
1994	9.91667
1995	7.70314
1996	10.51493
1997	32.11977
1998	17.9997
1999	21.35112
2000	13.93977
2001	6.52161
2002	5.73013
2003	8.52564
2004	8.88362
2005	6.0224
2006	3.63369
2007	1.32939
2008	1.41397
2009	2.47283
2010	2.75728
2011	1.7563
2012	2.50249
2013	2.4797
2014	2.70931
2015	4.41712
2016	3.65979