Year	Percent
1986-01-01	74.3955553852589
1987-01-01	72.5668044249610
1988-01-01	66.2750521346782
1989-01-01	62.9790230081520
1990-01-01	61.4104466517119
1991-01-01	56.1979625048319
1992-01-01	54.8729240344242
1993-01-01	55.5461017103536
1994-01-01	58.7578679849064
1995-01-01	62.4333042208932
1996-01-01	61.4970806350234
1997-01-01	60.0567502588241
1998-01-01	56.9546350621941
1999-01-01	56.5120124376745
2000-01-01	56.2342449775267
2001-01-01	58.0183190007732
2002-01-01	58.8500084079255
2003-01-01	58.5254673093164
2004-01-01	59.8176893803226
2005-01-01	59.3680332893829
2006-01-01	60.9323139430140
2007-01-01	60.3319141090365
2008-01-01	58.0892486222939
2009-01-01	53.5119717206299
2010-01-01	51.0900656313754
2011-01-01	50.6702697039645
2012-01-01	50.3042848066102
2013-01-01	50.8858119020228
2014-01-01	53.9463784984806
2015-01-01	54.9629804131508
2016-01-01	56.4633404991851
2017-01-01	57.3305293129632