Year Percent 1990-01-01 2.0180300000000000 1991-01-01 1.8644900000000002 1992-01-01 2.0504599999999997 1993-01-01 2.7506800000000000 1994-01-01 3.4557000000000000 1995-01-01 2.4467100000000000 1996-01-01 2.4548900000000002 1997-01-01 2.8923600000000000 1998-01-01 4.0921100000000000 1999-01-01 4.0341400000000000 2000-01-01 4.5295200000000000 2001-01-01 3.0556000000000000 2002-01-01 1.6635000000000000 2003-01-01 1.3822700000000000 2004-01-01 1.1405299999999998 2005-01-01 1.5839000000000000 2006-01-01 2.7815500000000000 2007-01-01 4.4946199999999990 2008-01-01 6.0665200000000000 2009-01-01 7.4942400000000000 2010-01-01 8.1362399999999990 2011-01-01 9.5405300000000000 2012-01-01 13.9825000000000000 2013-01-01 15.7682000000000000 2014-01-01 15.8212000000000000 2015-01-01 16.1593000000000000 2016-01-01 17.5584000000000000