Year	Percent
1968-01-01	53.3898421779654
1969-01-01	52.8675102951594
1970-01-01	53.5167934768759
1971-01-01	52.9166562310627
1972-01-01	50.7373740950028
1973-01-01	50.1865509135330
1974-01-01	47.1188313508436
1975-01-01	45.6611245470286
1976-01-01	44.3178748451436
1977-01-01	44.8075951691464
1978-01-01	44.6408863032877
1979-01-01	44.3464645581266
1980-01-01	43.9666425959228
1981-01-01	43.9331945476042
1982-01-01	43.5712086231892
1983-01-01	44.5048139235389
1984-01-01	44.3723832243984
1985-01-01	43.4092877332840
1986-01-01	43.8167032614791
1987-01-01	43.2542249874161
1988-01-01	43.3214757698469
1989-01-01	44.2006048616363
1990-01-01	44.9307967895571
1991-01-01	45.9133169574794
1992-01-01	46.5486534367012
1993-01-01	46.7097283950010
1994-01-01	47.2437536657552
1995-01-01	47.2838344903044
1996-01-01	47.6281642936884
1997-01-01	47.6518180805389
1998-01-01	47.7422188831756
1999-01-01	46.8637650070924
2000-01-01	46.8082325199137
2001-01-01	46.4170789466006
2002-01-01	44.9353008844852
2003-01-01	44.5444530654839
2004-01-01	44.4122481604804
2005-01-01	45.0921685749439
2006-01-01	45.2340446553784
2007-01-01	44.7125733984269
2008-01-01	44.6593579593546
2009-01-01	44.5980112835754
2010-01-01	43.7071723615871
2011-01-01	43.3806456599069
2012-01-01	41.9997983397875
2013-01-01	43.1562347676862
2014-01-01	43.2431669490905
2015-01-01	42.9188885561487
2016-01-01	44.5578156289289
2017-01-01	45.0386528353434