Year Percent 2000-01-01 59.5943534071968 2001-01-01 59.7563418932101 2002-01-01 60.5907663737694 2003-01-01 58.9859515242388 2004-01-01 60.1704711881552 2005-01-01 59.7854548291764 2006-01-01 59.7606465729259 2007-01-01 60.9015937083457 2008-01-01 61.3438699016819 2009-01-01 61.2240708318584 2010-01-01 62.4471177457530 2011-01-01 63.8679893246059 2012-01-01 64.6928071727327 2013-01-01 65.7525921970042 2014-01-01 67.4340856764954 2015-01-01 67.8845905858633 2016-01-01 68.0438233133942 2017-01-01 69.1361338960014