Year	Percent
1960	3.58621
1961	4.10933
1962	4.3213
1963	4.43431
1964	4.44723
1965	4.35653
1966	4.25305
1967	4.17687
1968	4.10493
1969	4.01239
1970	5.72524
1971	10.29354
1972	9.11515
1973	8.01574
1974	7.07213
1975	6.26344
1976	5.56515
1977	4.96091
1978	4.46543
1979	4.04925
1980	3.31255
1981	1.95359
1982	1.95655
1983	1.96344
1984	1.95405
1985	1.93611
1986	1.91392
1987	1.87171
1988	1.86103
1989	1.87357
1990	2.06727
1991	2.62166
1992	2.60356
1993	2.53593
1994	2.37868
1995	2.17351
1996	1.95398
1997	1.74839
1998	1.54216
1999	1.32395
2000	1.08637
2001	0.79939
2002	0.60236
2003	0.45025
2004	0.34955
2005	0.29508
2006	0.2579
2007	0.23175
2008	0.21314
2009	0.22137
2010	0.23021
2011	0.24165
2012	0.27887
2013	0.34287
2014	0.45885
2015	0.60397
2016	0.76463
2017	0.90167