Year	Percent
1977-01-01	24.2315940947021
1978-01-01	23.1054308206347
1979-01-01	22.1496807648581
1980-01-01	21.3688226758914
1981-01-01	20.7177740910125
1982-01-01	20.2135089225785
1983-01-01	19.8927467482303
1984-01-01	19.2653079915478
1985-01-01	18.5500394035386
1986-01-01	17.9895823333240
1987-01-01	17.4648404388548
1988-01-01	17.1188545223440
1989-01-01	16.5695317697499
1990-01-01	16.5017790483758
1991-01-01	16.6176601562145
1992-01-01	16.3783204559387
1993-01-01	16.5830378812221
1994-01-01	16.6209912898757
1995-01-01	16.5353627590999
1996-01-01	16.2077318809980
1997-01-01	15.8796461506625
1998-01-01	15.9492502657149
1999-01-01	15.8923127356714
2000-01-01	15.9645870576231
2001-01-01	16.2940678937490
2002-01-01	16.6758237873796
2003-01-01	17.0170891159436
2004-01-01	17.2495684765022
2005-01-01	17.2362822808500
2006-01-01	17.0705926729963
2007-01-01	16.9797920516325
2008-01-01	16.9160448918416
2009-01-01	17.3798512566537
2010-01-01	17.8385596908594
2011-01-01	18.4121822415244
2012-01-01	18.5506820123262
2013-01-01	18.9946041166656
2014-01-01	19.0696616022710
2015-01-01	19.1485023670932
2016-01-01	18.6966647834591
2017-01-01	18.3090773892005