Year	Percent
1991-01-01	13.0150728057418
1992-01-01	12.1913277667696
1993-01-01	12.0768376798608
1994-01-01	12.4144245106224
1995-01-01	13.1616848252946
1996-01-01	13.4762951005374
1997-01-01	13.8718028669020
1998-01-01	15.0315165557011
1999-01-01	15.6090408055131
2000-01-01	14.9741793430483
2001-01-01	14.7812506664496
2002-01-01	14.8256057138415
2003-01-01	14.6427045004762
2004-01-01	14.0425033905466
2005-01-01	13.4492182828538
2006-01-01	13.0565734186363
2007-01-01	12.4358306684943
2008-01-01	13.1880796020710
2009-01-01	13.9780125989063
2010-01-01	13.6589181797055
2011-01-01	13.5779916277239
2012-01-01	13.8687006207961
2013-01-01	13.8370748636809
2014-01-01	14.0332396159530
2015-01-01	14.6432948332081
2016-01-01	15.5885240661919
2017-01-01	15.9302914349452