Year	Percent
1961	1.35184
1962	0.38317
1963	3.27456
1964	1.98988
1965	2.95412
1966	4.37209
1967	4.02641
1968	3.79775
1969	7.58733
1970	4.28767
1971	6.00672
1972	11.0551
1973	18.41364
1974	15.9353
1975	10.82002
1976	10.44006
1977	11.16363
1978	11.61179
1979	15.06611
1980	24.87883
1981	10.13395
1982	13.98494
1983	16.52224
1984	11.47756
1985	16.81518
1986	17.15232
1987	14.479
1988	15.14927
1989	17.22452
1990	15.47712
1991	15.6519
1992	14.56777
1993	12.98156
1994	9.52482
1995	10.19676
1996	7.89872
1997	7.93802
1998	7.76837
1999	7.07195
2000	8.84379
2001	7.60466
2002	12.24055
2003	5.79357
2004	6.52701
2005	5.44905
2006	6.25538
2007	8.84941
2008	8.8315
2009	7.50453
2010	6.35098
2011	6.53224
2012	5.28278
2013	6.15527
2014	5.54699
2015	5.12138
2016	6.77384
2017	5.53671