Year	Percent
1968-01-01	5.0300800000000000
1969-01-01	4.2783100000000000
1970-01-01	4.2093900000000000
1971-01-01	4.7115900000000000
1972-01-01	5.0406600000000000
1973-01-01	5.8372900000000000
1974-01-01	6.5324900000000000
1975-01-01	6.6929000000000000
1976-01-01	6.7333700000000000
1977-01-01	7.0683200000000000
1978-01-01	7.4145500000000000
1979-01-01	8.0028800000000010
1980-01-01	8.6488300000000000
1981-01-01	9.8108700000000000
1982-01-01	11.4867000000000000
1983-01-01	13.0941000000000000
1984-01-01	14.0563000000000000
1985-01-01	14.2622000000000000
1986-01-01	13.2608000000000000
1987-01-01	12.1908000000000000
1988-01-01	11.6555000000000000
1989-01-01	12.1308000000000000
1990-01-01	12.1487000000000000
1991-01-01	11.7808000000000000
1992-01-01	11.6449000000000000
1993-01-01	11.3715000000000000
1994-01-01	12.0794000000000000
1995-01-01	12.8061000000000000
1996-01-01	12.4576000000000000
1997-01-01	11.8259999999999990
1998-01-01	12.1340000000000000
1999-01-01	11.1733000000000000
2000-01-01	9.5792100000000000
2001-01-01	8.7126600000000010
2002-01-01	6.8879500000000000
2003-01-01	5.1453700000000000
2004-01-01	3.5142599999999997
2005-01-01	3.4515300000000004
2006-01-01	3.3519400000000004
2007-01-01	3.3123699999999996
2008-01-01	3.7040500000000000
2009-01-01	3.1662300000000000
2010-01-01	2.5094700000000000
2011-01-01	2.5323000000000000
2012-01-01	2.8756700000000000
2013-01-01	3.0245500000000000
2014-01-01	3.0786800000000000
2015-01-01	3.1365900000000000
2016-01-01	3.1304100000000000