Year	Percent
1986-01-01	49.7473355709836
1987-01-01	48.0513295467039
1988-01-01	46.3565782045306
1989-01-01	43.5310732878209
1990-01-01	43.6707782705739
1991-01-01	43.8703163523713
1992-01-01	44.4559897444816
1993-01-01	47.1100107162174
1994-01-01	49.4889982373930
1995-01-01	51.9007137988786
1996-01-01	55.6645776717389
1997-01-01	56.6233729997251
1998-01-01	58.1066952725496
1999-01-01	59.5948226243890
2000-01-01	59.6681418530090
2001-01-01	62.5956469369240
2002-01-01	65.3531162385148
2003-01-01	66.7480821968490
2004-01-01	68.7404133898754
2005-01-01	70.8451780665432
2006-01-01	71.4852009542952
2007-01-01	72.8520039973466
2008-01-01	73.0760492102572
2009-01-01	74.3008587661312
2010-01-01	75.6649111724589
2011-01-01	75.9261646028869
2012-01-01	76.7285637556679
2013-01-01	77.1438888294819
2014-01-01	78.5138028240178
2015-01-01	77.8125390440076
2016-01-01	78.5698790077741
2017-01-01	80.4876585774847