Year Percent 1980-01-01 0.25947900000000000 1981-01-01 0.24253300000000000 1982-01-01 0.36248600000000003 1983-01-01 0.45389900000000000 1984-01-01 0.31868900000000000 1985-01-01 0.37696700000000000 1986-01-01 0.46096499999999996 1987-01-01 0.46206800000000003 1988-01-01 0.31275400000000000 1989-01-01 0.16579900000000000 1990-01-01 0.15787400000000001 1991-01-01 0.19908199999999998 1992-01-01 0.16980499999999998 1993-01-01 1.33283000000000000 1994-01-01 3.35270000000000000 1995-01-01 4.76498000000000000 1996-01-01 6.78830000000000000 1997-01-01 10.06370000000000000 1998-01-01 14.05330000000000000 1999-01-01 14.70940000000000000 2000-01-01 12.68080000000000000 2001-01-01 13.31260000000000000 2002-01-01 16.66590000000000000 2003-01-01 15.80980000000000000 2004-01-01 17.77120000000000000 2005-01-01 16.67640000000000000 2006-01-01 16.53170000000000000 2007-01-01 14.02950000000000000 2008-01-01 12.11990000000000000 2009-01-01 14.91770000000000000 2010-01-01 14.30850000000000000 2011-01-01 12.35280000000000000 2012-01-01 14.69090000000000000 2013-01-01 15.03350000000000000 2014-01-01 14.80960000000000000 2015-01-01 18.33810000000000000 2016-01-01 19.54720000000000000