Year	Percent
1999-01-01	18.77
2000-01-01	19.69
2001-01-01	19.09
2002-01-01	19.82
2003-01-01	21.39
2004-01-01	22.02
2005-01-01	25.29
2006-01-01	30.15
2007-01-01	31.23
2008-01-01	31.71
2009-01-01	33.11
2010-01-01	32.61
2011-01-01	29.24
2012-01-01	30.97
2013-01-01	31.08
2014-01-01	31.81
2015-01-01	30.01
2016-01-01	27.79