Year Percent 1991-01-01 35.0069999694824 1992-01-01 37.2970008850098 1993-01-01 42.3800010681152 1994-01-01 49.0279998779297 1995-01-01 51.3050003051758 1996-01-01 52.6469993591309 1997-01-01 52.1969985961914 1998-01-01 53.1879997253418 1999-01-01 57.3089981079102 2000-01-01 51.6739997863770 2001-01-01 52.2529983520508 2002-01-01 55.3180007934570 2003-01-01 56.3260002136230 2004-01-01 59.3479995727539 2005-01-01 59.9080009460449 2006-01-01 62.4199981689453 2007-01-01 58.6399993896484 2008-01-01 47.2999992370605 2009-01-01 50.3720016479492 2010-01-01 57.3400001525879 2011-01-01 58.5180015563965 2012-01-01 59.7550010681152 2013-01-01 58.8160018920898 2014-01-01 62.6599998474121 2015-01-01 62.3180007934570 2016-01-01 54.3100013732910 2017-01-01 54.8909988403320