Year Percent 1990-01-01 51.905100000000000 1991-01-01 53.495300000000000 1992-01-01 54.443900000000000 1993-01-01 55.602600000000000 1994-01-01 59.751999999999995 1995-01-01 63.572800000000000 1996-01-01 61.454900000000000 1997-01-01 57.806600000000000 1998-01-01 57.634800000000000 1999-01-01 51.712300000000000 2000-01-01 50.468000000000000 2001-01-01 47.230800000000000 2002-01-01 55.127700000000000 2003-01-01 54.287700000000000 2004-01-01 57.208900000000000 2005-01-01 39.441200000000000 2006-01-01 36.668400000000000 2007-01-01 31.613900000000000 2008-01-01 29.807700000000000 2009-01-01 33.601900000000000 2010-01-01 36.280400000000000 2011-01-01 39.774400000000000 2012-01-01 44.760300000000000 2013-01-01 41.391000000000005 2014-01-01 39.869000000000000 2015-01-01 38.257900000000000 2016-01-01 36.634800000000000