Year	Percent
1995-01-01	18
1996-01-01	18
1997-01-01	18
1998-01-01	18
1999-01-01	18
2000-01-01	18
2001-01-01	18
2002-01-01	18
2003-01-01	18
2004-01-01	18
2005-01-01	18
2006-01-01	18
2007-01-01	18
2008-01-01	21
2009-01-01	22
2010-01-01	22
2011-01-01	22
2012-01-01	22
2013-01-01	22