Year	Percent
1995-01-01	18
1996-01-01	17
1997-01-01	18
1998-01-01	18
1999-01-01	22
2000-01-01	23
2001-01-01	18
2002-01-01	15
2003-01-01	15
2004-01-01	15
2005-01-01	15
2006-01-01	15
2007-01-01	15
2008-01-01	16
2009-01-01	20
2010-01-01	25
2011-01-01	25
2012-01-01	25
2013-01-01	22