Year	Percent
1977-01-01	33.3500970533651
1978-01-01	31.8333077518350
1979-01-01	31.3472036755605
1980-01-01	31.9317410995266
1981-01-01	32.2567805315950
1982-01-01	32.7710206568142
1983-01-01	32.8562789806415
1984-01-01	32.2700122681128
1985-01-01	31.7304008937078
1986-01-01	31.3999605145420
1987-01-01	31.6024844093476
1988-01-01	31.6283975096454
1989-01-01	31.4118620149249
1990-01-01	32.6911670617156
1991-01-01	33.9649594986743
1992-01-01	33.8627110083562
1993-01-01	33.9162168952926
1994-01-01	33.5870683391249
1995-01-01	33.7291156449790
1996-01-01	34.4971522195906
1997-01-01	34.5616340235429
1998-01-01	34.1323807120610
1999-01-01	34.5187368318620
2000-01-01	34.1931966415218
2001-01-01	35.4559230757099
2002-01-01	36.7198442624262
2003-01-01	38.4453570664156
2004-01-01	38.8623720225623
2005-01-01	39.2294422945936
2006-01-01	39.3868270481229
2007-01-01	40.5933101710388
2008-01-01	41.2147255724671
2009-01-01	43.1353154709600
2010-01-01	44.8269723562520
2011-01-01	45.0265494632842
2012-01-01	45.1180189944266
2013-01-01	44.9537533718417
2014-01-01	44.9952025470190
2015-01-01	44.9930966772190
2016-01-01	44.8272001186948
2017-01-01	44.5273199418818