Year	Percent
1961	13.28273
1962	11.14783
1963	8.22559
1964	16.18152
1965	12.31317
1966	10.43977
1967	2.7632
1968	13.71309
1969	20.87388
1997	4.46121
1998	4.72106
1999	3.49996
2000	4.01506
2001	8.67861
2002	5.89034
2003	0.48501
2004	2.67168
2005	2.58344
2006	8.37608
2007	4.30528
2008	11.86454
2009	10.22027
2010	5.47244
2011	2.96956
2012	3.28349
2013	1.87591
2014	4.07248
2015	6.04183
2016	2.11304
2017	0.48196