Year	Percent
1991-01-01	14.9619998931885
1992-01-01	24.4850006103516
1993-01-01	30.7900009155273
1994-01-01	31.1539993286133
1995-01-01	40.6049995422363
1996-01-01	41.2270011901855
1997-01-01	35.2550010681152
1998-01-01	34.3930015563965
1999-01-01	29.8390007019043
2000-01-01	29.6739997863770
2001-01-01	27.7399997711182
2002-01-01	29.3959999084473
2003-01-01	28.8150005340576
2004-01-01	28.3209991455078
2005-01-01	19.9629993438721
2006-01-01	18.6189994812012
2007-01-01	16.4169998168945
2008-01-01	16.3369998931885
2009-01-01	21.3819999694824
2010-01-01	21.2649993896484
2011-01-01	19.9370002746582
2012-01-01	18.8579998016357
2013-01-01	19.7929992675781
2014-01-01	20.3939990997314
2015-01-01	22.2900009155273
2016-01-01	20.0100002288818
2017-01-01	20.0400009155273