Year	Percent
1974	3.8841
1975	5.05304
1976	6.8917
1977	11.46809
1978	13.81392
1979	7.39154
1980	6.29574
1981	8.24672
1982	10.66321
1983	11.56013
1984	14.07747
1985	30.37506
1986	21.79293
1987	21.22831
1988	24.77608
1989	15.05448
1990	12.55677
1991	7.38952
1992	9.06872
1993	8.74551
1994	8.93277
1995	7.02515
1996	8.88839
1997	7.42473
1998	7.15068
1999	5.00148
2000	5.63645
2001	5.97236
2002	7.18494
2003	7.85386
2004	6.19389
2005	5.62669
2006	3.81405
2007	3.87758
2008	2.4157
2009	5.10358
2010	2.3823
2011	2.37606
2012	2.49962
2013	4.50723
2014	4.86522
2015	6.07824
2016	4.898