Year	Percent
1975-01-01	1.490
1976-01-01	1.230
1977-01-01	1.230
1978-01-01	1.160
1979-01-01	2.005
1980-01-01	2.180
1981-01-01	2.010
1982-01-01	1.325
1983-01-01	1.750
1984-01-01	2.410
1985-01-01	2.735
1986-01-01	4.750
1987-01-01	8.190
1988-01-01	8.450
1989-01-01	5.310
1990-01-01	5.770
1991-01-01	5.280
1992-01-01	4.160
1993-01-01	3.920
1994-01-01	4.190
1995-01-01	2.935
1996-01-01	3.040
1997-01-01	4.950
1998-01-01	5.730
1999-01-01	5.360
2000-01-01	4.430
2001-01-01	3.720
2002-01-01	3.160
2003-01-01	2.275
2004-01-01	2.360
2005-01-01	3.620
2006-01-01	4.710
2007-01-01	8.455
2008-01-01	6.870
2009-01-01	5.470
2010-01-01	4.090
2011-01-01	3.200
2012-01-01	3.020
2013-01-01	6.370
2014-01-01	9.140
2015-01-01	9.740