Year	Percent
1991-01-01	40.5309982299805
1992-01-01	40.2260017395020
1993-01-01	39.9729995727539
1994-01-01	39.6650009155273
1995-01-01	39.3730010986328
1996-01-01	39.0540008544922
1997-01-01	38.7519989013672
1998-01-01	38.5810012817383
1999-01-01	38.4329986572266
2000-01-01	38.4700012207031
2001-01-01	38.4399986267090
2002-01-01	39.4550018310547
2003-01-01	40.6800003051758
2004-01-01	41.8320007324219
2005-01-01	41.6790008544922
2006-01-01	41.1879997253418
2007-01-01	40.6059989929199
2008-01-01	38.7309989929199
2009-01-01	38.5550003051758
2010-01-01	37.3240013122559
2011-01-01	37.4879989624023
2012-01-01	37.1920013427734
2013-01-01	37.6160011291504
2014-01-01	37.2299995422363
2015-01-01	38.0629997253418
2016-01-01	38.8240013122559
2017-01-01	38.6240005493164