Year	Percent
1979-01-01	36.1524524461094
1980-01-01	33.8247249979422
1981-01-01	34.4827092431528
1982-01-01	34.6233740596633
1983-01-01	34.1282353585347
1984-01-01	33.8319014082449
1985-01-01	33.2455525602051
1986-01-01	32.0173222013215
1987-01-01	32.3241907006888
1988-01-01	32.6768121161816
1989-01-01	31.2883883410400
1990-01-01	31.1445333254870
1991-01-01	33.3124338065247
1992-01-01	33.5152493795726
1993-01-01	34.2789480090594
1994-01-01	31.8582230949482
1995-01-01	30.4447579893129
1996-01-01	30.5199562325225
1997-01-01	32.4853076434803
1998-01-01	32.3944038903495
1999-01-01	32.0333898334471
2000-01-01	31.5463942694896
2001-01-01	30.9342338074025
2002-01-01	31.7765912398637
2003-01-01	30.9901840336354
2004-01-01	30.9250466148009
2005-01-01	30.4325062240434
2006-01-01	30.5132687091439
2007-01-01	30.3098037730462
2008-01-01	30.5230493829319
2009-01-01	32.2679567616129
2010-01-01	32.8095497061656
2011-01-01	32.5281986785801
2012-01-01	33.2160577484018
2013-01-01	33.7353939085522
2014-01-01	33.7482058670859
2015-01-01	33.2765028197482
2016-01-01	33.6391002705210
2017-01-01	33.6591839699126