Year	Percent
1991-01-01	17.6389999389648
1992-01-01	18.2789993286133
1993-01-01	18.4710006713867
1994-01-01	18.7129993438721
1995-01-01	16.6420001983643
1996-01-01	17.1620006561279
1997-01-01	17.3990001678467
1998-01-01	17.4839992523193
1999-01-01	17.3920001983643
2000-01-01	20.7539997100830
2001-01-01	24.2479991912842
2002-01-01	27.1580009460449
2003-01-01	30.0760002136230
2004-01-01	34.2529983520508
2005-01-01	35.7480010986328
2006-01-01	38.5999984741211
2007-01-01	40.4570007324219
2008-01-01	39.9990005493164
2009-01-01	37.7700004577637
2010-01-01	38.6940002441406
2011-01-01	34.0079994201660
2012-01-01	35.0740013122559
2013-01-01	34.7290000915527
2014-01-01	35.1510009765625
2015-01-01	35.5880012512207
2016-01-01	35.7420005798340
2017-01-01	35.9480018615723