Year Percent 1991-01-01 0.953 1992-01-01 1.026 1993-01-01 1.305 1994-01-01 1.598 1995-01-01 1.393 1996-01-01 1.780 1997-01-01 2.432 1998-01-01 3.252 1999-01-01 4.271 2000-01-01 5.100 2001-01-01 6.060 2002-01-01 7.090 2003-01-01 7.770 2004-01-01 8.360 2005-01-01 9.090 2006-01-01 10.190 2007-01-01 10.700 2008-01-01 10.800 2009-01-01 10.210 2010-01-01 10.040 2011-01-01 9.330 2012-01-01 9.990 2013-01-01 10.120 2014-01-01 10.390 2015-01-01 10.020 2016-01-01 10.000