Year	Percent
1977-01-01	33.3502297334590
1978-01-01	31.8316602232090
1979-01-01	31.3549694636529
1980-01-01	31.9490409037194
1981-01-01	32.2623423373615
1982-01-01	32.7783195812982
1983-01-01	32.8476532645557
1984-01-01	32.2710406706923
1985-01-01	31.7351973089583
1986-01-01	31.4009971691917
1987-01-01	31.6033227647317
1988-01-01	31.6286465268164
1989-01-01	31.4069795344369
1990-01-01	32.7013418640361
1991-01-01	33.9689021591433
1992-01-01	33.8651106980741
1993-01-01	33.9288271835701
1994-01-01	33.6008586218911
1995-01-01	33.7402653742975
1996-01-01	34.5035236923431
1997-01-01	34.5730200906275
1998-01-01	34.1300850256804
1999-01-01	34.5231093749685
2000-01-01	34.1943241024539
2001-01-01	35.4712436442200
2002-01-01	36.7136038213055
2003-01-01	38.4422587021634
2004-01-01	38.8571826090304
2005-01-01	39.2208273969223
2006-01-01	39.3857453290619
2007-01-01	40.6120687135271
2008-01-01	41.2233128698758
2009-01-01	43.1408088312161
2010-01-01	44.8340935767376
2011-01-01	45.0310968841770
2012-01-01	45.1191526215838
2013-01-01	44.9511692214416
2014-01-01	44.9920350753182
2015-01-01	45.0025841286789
2016-01-01	44.8349910160969
2017-01-01	44.5337234557519