Year	Percent
1986-01-01	28.6877091796906
1987-01-01	29.0598704397933
1988-01-01	30.1435750067925
1989-01-01	30.5008512309222
1990-01-01	30.8682330167668
1991-01-01	30.7591141027801
1992-01-01	31.8996236712729
1993-01-01	34.1045961552370
1994-01-01	34.3120552801373
1995-01-01	33.9578776382419
1996-01-01	33.9099439002767
1997-01-01	34.5876942951649
1998-01-01	35.1059690874682
1999-01-01	35.6629932419415
2000-01-01	35.5683475496256
2001-01-01	34.9512215375076
2002-01-01	35.0071643439834
2003-01-01	36.5529454773125
2004-01-01	38.1419720477064
2005-01-01	39.2562436866927
2006-01-01	38.4927634931840
2007-01-01	39.1110696942892
2008-01-01	40.8702824061675
2009-01-01	41.2861659511591
2010-01-01	45.3318475384050
2011-01-01	47.3459012245464
2012-01-01	47.5984134963628
2013-01-01	47.7159454428802
2014-01-01	48.4129038046268
2015-01-01	48.2305761075937
2016-01-01	48.0313550267192
2017-01-01	48.5325570108058