Year	Percent
1973	9.4248
1974	7.6128
1975	7.92265
1976	8.80519
1977	10.45648
1978	10.00943
1979	10.21142
1980	9.61175
1981	9.92771
1982	9.83102
1983	9.2367
1984	8.58444
1985	8.25519
1986	7.41174
1987	6.36554
1988	4.49353
1989	4.26179
1990	6.19778
1991	5.61021
1992	5.0374
1993	4.72801
1994	4.25171
1995	3.74449
1996	3.95932
1997	4.41524
1998	3.51931
1999	2.75275
2000	2.96651
2001	2.25714
2002	2.00105
2003	2.21041
2004	3.27246
2005	3.88178
2012	4.52409
2013	5.52957
2014	5.8358
2015	6.00603
2016	6.40925
2017	5.82148