Year	Percent
1991-01-01	21.1180000305176
1992-01-01	20.8099994659424
1993-01-01	20.1410007476807
1994-01-01	19.5650005340576
1995-01-01	18.7250003814697
1996-01-01	17.7679996490479
1997-01-01	19.7110004425049
1998-01-01	21.2479991912842
1999-01-01	23.0240001678467
2000-01-01	24.3320007324219
2001-01-01	26.4769992828369
2002-01-01	24.3659992218018
2003-01-01	21.6860008239746
2004-01-01	19.6250000000000
2005-01-01	23.7759990692139
2006-01-01	22.5279998779297
2007-01-01	21.8969993591309
2008-01-01	22.6550006866455
2009-01-01	24.3589992523193
2010-01-01	28.3190002441406
2011-01-01	26.5919990539551
2012-01-01	27.0450000762939
2013-01-01	23.6849994659424
2014-01-01	24.8789997100830
2015-01-01	25.8379993438721
2016-01-01	28.8069992065430
2017-01-01	29.9360008239746