Year	Percent
1975	11.95347
1976	10.4512
1977	13.68826
1978	21.07062
1979	19.66844
1980	18.86229
1981	20.2649
1982	20.60409
1983	23.98845
1984	25.70641
1985	31.91543
1986	30.12208
1987	21.94053
1988	20.20168
1989	16.36572
1990	16.92316
1991	13.00764
1992	13.76669
1993	12.98338
1994	13.42323
1995	11.60362
1996	12.64538
1997	15.51721
1998	18.42586
1999	21.80775
2000	16.29499
2001	25.38481
2002	23.24549
2003	15.54159
2004	10.98769
2005	13.69695
2006	9.3999
2007	11.77121
2008	7.95854
2009	6.82921
2010	4.70784
2011	3.88678
2012	5.37314
2013	4.40127
2014	5.17234
2015	6.86893
2016	4.98209