Year	Percent
1962-01-01	2.110
1963-01-01	1.760
1964-01-01	1.380
1965-01-01	1.150
1966-01-01	0.115
1967-01-01	0.190
1968-01-01	0.100
1969-01-01	0.110
1970-01-01	0.095
1971-01-01	0.200
1972-01-01	0.600
1973-01-01	0.780
1974-01-01	0.840
1975-01-01	0.845
1976-01-01	0.980
1977-01-01	0.960
1978-01-01	1.050
1979-01-01	1.240
1980-01-01	1.320
1981-01-01	1.230
1982-01-01	1.635
1983-01-01	1.690
1984-01-01	2.040
1985-01-01	2.740
1986-01-01	3.190
1987-01-01	3.110
1988-01-01	2.950
1989-01-01	2.815
1990-01-01	3.430
1991-01-01	3.555
1992-01-01	4.340
1993-01-01	5.755
1994-01-01	6.850
1995-01-01	4.535
1996-01-01	4.250
1997-01-01	6.020
1998-01-01	7.020
1999-01-01	7.580
2000-01-01	7.880
2001-01-01	8.635
2002-01-01	8.880
2003-01-01	8.420
2004-01-01	7.550
2005-01-01	6.870
2006-01-01	6.620
2007-01-01	7.030
2008-01-01	6.420
2009-01-01	7.135
2010-01-01	6.905
2011-01-01	6.375
2012-01-01	6.955
2013-01-01	8.480
2014-01-01	13.660
2015-01-01	16.520