Year Percent 1994-01-01 0.3847800000000000 1995-01-01 0.8597070000000000 1996-01-01 1.4078700000000002 1997-01-01 2.6956300000000000 1998-01-01 5.2184300000000010 1999-01-01 7.3738300000000000 2000-01-01 14.2354000000000000 2001-01-01 19.6104000000000000 2002-01-01 18.2559000000000000 2003-01-01 16.3899000000000000 2004-01-01 18.2494000000000000 2005-01-01 21.8207000000000000 2006-01-01 19.3361000000000000 2007-01-01 17.3230000000000000 2008-01-01 15.6911000000000000 2009-01-01 15.9468000000000000 2010-01-01 15.4615000000000000 2011-01-01 15.9569000000000000 2012-01-01 15.9070000000000000