Year	Percent
1971	13.25429
1972	9.98595
1973	10.01705
1974	8.50859
1975	9.00113
1976	12.19619
1977	18.23033
1978	12.89693
1979	10.73629
1980	9.94851
1981	14.53635
1982	10.63272
1983	9.07517
1984	11.08982
1985	14.28947
1986	17.278
1987	20.22881
1988	22.72252
1989	23.87812
1990	11.88058
1991	13.9221
1992	7.19575
1993	6.50885
1994	5.81878
1995	54.68185
1996	16.19311
1997	10.24848
1998	8.97587
1999	9.88367
2000	9.20866
2001	6.26874
2002	7.00237
2003	11.50753
2004	19.52985
2005	9.54733
2006	8.50063
2007	10.38033
2008	6.13814
2009	4.2251
2010	12.51565
2011	0.38313
2012	0.26074
2013	0.65672
2014	1.31787
2015	1.91672
2016	5.24107