Year	Percent
1974	5.2372
1975	4.12177
1976	3.5853
1977	2.35051
1978	3.0845
1979	3.57791
1980	8.36465
1981	4.85773
1982	12.91912
1983	17.58434
1984	16.36826
1985	14.36706
1986	16.15398
1987	8.85975
1988	9.15108
1989	8.81142
1990	9.86428
1991	5.56573
1992	5.13019
1993	5.44843
1994	7.08268
1995	7.51405
1996	6.36924
1997	9.16212
1998	9.96897
1999	10.99504
2000	13.64478
2001	8.65338
2002	8.99476
2003	5.24025
2004	5.03326
2005	6.00426
2006	4.24382
2007	2.60276
2008	3.72481
2009	3.55684
2010	3.2928
2011	4.01343
2012	4.32357
2013	3.35309
2014	2.61193
2015	3.54808