Year	Percent
1986-01-01	26.5618246963648
1987-01-01	26.5527879149404
1988-01-01	25.2368271627289
1989-01-01	24.1500638744439
1990-01-01	24.4452575393959
1991-01-01	24.2716069372824
1992-01-01	24.4135718833313
1993-01-01	22.7745632960827
1994-01-01	22.4726322383300
1995-01-01	23.3478356786362
1996-01-01	24.5578210270402
1997-01-01	25.3088579669323
1998-01-01	25.2386512035832
1999-01-01	25.3580741432339
2000-01-01	26.0924447743951
2001-01-01	26.5721653452539
2002-01-01	26.9906331178336
2003-01-01	27.0541432551219
2004-01-01	27.4968987517968
2005-01-01	27.5757988753617
2006-01-01	28.3280632446114
2007-01-01	28.6259013275841
2008-01-01	28.2147594949207
2009-01-01	29.0058043905971
2010-01-01	27.9128926430394
2011-01-01	27.2893883042385
2012-01-01	28.0740228570072
2013-01-01	28.1957916286623
2014-01-01	28.4214615606003
2015-01-01	28.5171866024507
2016-01-01	28.7329751810528
2017-01-01	28.7729536130080