Year	Percent
1991-01-01	18.9087068137527
1992-01-01	20.0018859127874
1993-01-01	23.0237917501801
1994-01-01	24.2761019754739
1995-01-01	23.3542327170831
1996-01-01	23.3162725903459
1997-01-01	22.1484540937752
1998-01-01	20.6374522259065
1999-01-01	20.8574348754484
2000-01-01	19.9305645794175
2001-01-01	18.9342417869605
2002-01-01	19.6145961616223
2003-01-01	19.6601494769068
2004-01-01	20.0670382214244
2005-01-01	19.9544906192036
2006-01-01	18.5418472316164
2007-01-01	16.4023944792889
2008-01-01	16.3106570733173
2009-01-01	20.8163410591921
2010-01-01	22.1540337257804
2011-01-01	23.1019966045721
2012-01-01	24.9548424484721
2013-01-01	25.8308447618170
2014-01-01	24.5160591323305
2015-01-01	22.6581639878768
2016-01-01	20.9624914886719
2017-01-01	18.8583257323632