Year Percent 1991-01-01 1.78299999237061 1992-01-01 1.81599998474121 1993-01-01 1.86300003528595 1994-01-01 1.84399998188019 1995-01-01 1.87100005149841 1996-01-01 2.31699991226196 1997-01-01 2.75500011444092 1998-01-01 3.24799990653992 1999-01-01 3.83100008964539 2000-01-01 4.38000011444092 2001-01-01 5.05999994277954 2002-01-01 5.49900007247925 2003-01-01 5.44399976730347 2004-01-01 6.69999980926514 2005-01-01 8.22799968719482 2006-01-01 7.02500009536743 2007-01-01 8.25800037384033 2008-01-01 8.68299961090088 2009-01-01 10.79800033569340 2010-01-01 10.11400032043460 2011-01-01 10.52099990844730 2012-01-01 12.00000000000000 2013-01-01 11.87600040435790 2014-01-01 12.88599967956540 2015-01-01 13.07600021362300 2016-01-01 13.52299976348880 2017-01-01 13.77999973297120