Year	Percent
1961	2.93881
1962	4.01932
1963	2.76322
1964	4.3965
1965	5.99375
1966	6.54988
1967	5.00825
1968	2.39186
1969	3.4174
1970	11.90008
1971	7.11029
1972	6.97317
1973	7.03377
1974	9.45815
1975	14.5124
1976	11.91897
1977	10.52957
1978	9.54907
1979	7.94321
1980	11.71651
1981	8.76734
1982	8.08461
1983	9.95406
1984	7.63598
1985	6.40451
1986	6.32272
1987	4.72095
1988	6.57121
1989	7.92467
1990	9.47382
1991	8.24679
1992	1.01534
1993	2.21227
1994	2.55774
1995	3.79843
1996	1.03931
1997	1.56926
1998	0.78048
1999	0.93503
2000	1.55879
2001	2.50488
2002	1.59556
2003	1.75812
2004	0.42924
2005	0.80368
2006	1.82112
2007	2.88491
2008	3.32182
2009	2.38314
2010	0.99094
2011	1.18424
2012	1.0612
2013	1.05543
2014	1.77737
2015	2.06562
2016	1.59325
2017	2.08727