Year Percent 1990-01-01 42.953700000000000 1991-01-01 50.898800000000000 1992-01-01 50.057200000000000 1993-01-01 48.430900000000000 1994-01-01 53.757900000000000 1995-01-01 54.230400000000000 1996-01-01 47.370800000000000 1997-01-01 41.523000000000000 1998-01-01 43.086000000000006 1999-01-01 43.601600000000000 2000-01-01 39.878500000000000 2001-01-01 28.868100000000000 2002-01-01 18.042600000000000 2003-01-01 16.614000000000000 2004-01-01 15.895400000000000 2005-01-01 23.948000000000000 2006-01-01 38.323100000000000 2007-01-01 56.444700000000000 2008-01-01 67.694200000000000 2009-01-01 65.398100000000000 2010-01-01 65.063500000000000 2011-01-01 71.001000000000000 2012-01-01 75.282000000000000 2013-01-01 79.848700000000000 2014-01-01 81.061700000000000 2015-01-01 81.657500000000000 2016-01-01 78.678500000000000