Year	Percent
1971	37.47169
1972	32.1537
1973	32.21463
1974	13.78268
1975	4.13866
1976	2.92316
1977	4.82673
1978	4.3493
1979	7.41556
1980	7.96071
1981	5.77227
1982	4.45384
1983	5.04944
1984	5.31286
1985	5.43201
1986	6.27432
1987	4.7617
1988	4.33947
1989	3.04492
1990	2.5408
1991	1.78134
1992	1.50908
1993	0.48605
1994	1.06659
1995	1.1891
1996	0.64301
1997	0.79679
1998	0.62486
1999	0.67809
2000	0.69824
2001	0.70978
2002	0.73398
2003	0.85417
2004	2.04801
2005	1.22678
2006	1.36284
2007	1.44893
2008	0.63166
2009	7.90229
2010	21.1484
2011	23.0136
2012	29.02845
2013	27.17254
2014	28.19152
2015	22.56675
2016	13.94858