Year	Percent
1991-01-01	33.9129981994629
1992-01-01	33.9850006103516
1993-01-01	30.4090003967285
1994-01-01	26.7600002288818
1995-01-01	26.2560005187988
1996-01-01	27.4839992523193
1997-01-01	26.8600006103516
1998-01-01	24.8260002136230
1999-01-01	22.6480007171631
2000-01-01	20.3759994506836
2001-01-01	22.5000000000000
2002-01-01	23.3239994049072
2003-01-01	23.4899997711182
2004-01-01	21.6100006103516
2005-01-01	23.8880004882813
2006-01-01	22.5620002746582
2007-01-01	22.0890007019043
2008-01-01	24.3990001678467
2009-01-01	31.0919990539551
2010-01-01	34.0279998779297
2011-01-01	33.2519989013672
2012-01-01	30.2709999084473
2013-01-01	29.9759998321533
2014-01-01	29.2390003204346
2015-01-01	25.2959995269775
2016-01-01	24.8999996185303
2017-01-01	22.9519996643066