Year	Percent
1991-01-01	20.9444615416522
1992-01-01	14.7686406689432
1993-01-01	16.3868863979823
1994-01-01	17.8281954608350
1995-01-01	21.6611012673906
1996-01-01	22.0031725937807
1997-01-01	22.8844040060689
1998-01-01	24.7808130650287
1999-01-01	23.2830423848968
2000-01-01	21.8543251195797
2001-01-01	21.0048429044027
2002-01-01	20.9789045439726
2003-01-01	22.2968290725562
2004-01-01	20.5953144328065
2005-01-01	18.4640428939879
2006-01-01	19.2440043708170
2007-01-01	16.6871476750431
2008-01-01	16.1557332045157
2009-01-01	19.3450223114210
2010-01-01	18.7800062072466
2011-01-01	18.0488836337710
2012-01-01	17.6499693680945
2013-01-01	17.3632427587832
2014-01-01	17.5858982453941