Year	Percent
1979-01-01	56.4182484850873
1980-01-01	55.2360199123388
1981-01-01	55.2553103442215
1982-01-01	55.3585915023907
1983-01-01	55.3405040918544
1984-01-01	54.7024081488649
1985-01-01	53.7248653635926
1986-01-01	51.7081085704799
1987-01-01	51.0648252072021
1988-01-01	50.1390598645250
1989-01-01	48.7757806300842
1990-01-01	47.7561517008161
1991-01-01	48.0211712365343
1992-01-01	48.0600336990415
1993-01-01	48.2993002758377
1994-01-01	47.4049937256387
1995-01-01	46.4007214764925
1996-01-01	46.2096365588052
1997-01-01	46.4180976671416
1998-01-01	46.3629781724075
1999-01-01	46.3727139124721
2000-01-01	45.4923849498088
2001-01-01	44.9512883382463
2002-01-01	44.7596001095267
2003-01-01	44.0852078254880
2004-01-01	44.3138212551738
2005-01-01	43.0310744983920
2006-01-01	42.4816084352163
2007-01-01	41.9313406213471
2008-01-01	41.4523825762585
2009-01-01	41.2532727282179
2010-01-01	41.3876267876173
2011-01-01	41.1360118751367
2012-01-01	41.2284301765248
2013-01-01	41.3094748837835
2014-01-01	41.3316502017395
2015-01-01	40.8746232538313
2016-01-01	40.6473852663815
2017-01-01	40.1490372976386