Year	Percent
1979-01-01	67.5350569257522
1980-01-01	66.9945921902490
1981-01-01	65.2533121951881
1982-01-01	63.2202185312473
1983-01-01	58.7794782394463
1984-01-01	58.2271628117940
1985-01-01	57.0492677700205
1986-01-01	58.1607373814363
1987-01-01	57.2051426459480
1988-01-01	57.4485384890680
1989-01-01	58.8105101245507
1990-01-01	58.7683184092012
1991-01-01	55.7959905296789
1992-01-01	54.2921083991458
1993-01-01	52.0631622426611
1994-01-01	54.3330485616255
1995-01-01	55.7309403476544
1996-01-01	55.0273420280329
1997-01-01	55.4296916688957
1998-01-01	56.1667730577185
1999-01-01	56.5429590743358
2000-01-01	57.6061352372036
2001-01-01	57.1829198113524
2002-01-01	58.8046341046101
2003-01-01	60.7837452227331
2004-01-01	62.1297765554621
2005-01-01	63.7491381471808
2006-01-01	64.9004307272013
2007-01-01	65.7452738223157
2008-01-01	65.5744173033919
2009-01-01	66.7268013156650
2010-01-01	68.5644448104443
2011-01-01	69.0342645841393
2012-01-01	69.0773392056531
2013-01-01	68.9775915581543
2014-01-01	69.0495758723233
2015-01-01	69.2642156891723
2016-01-01	68.4774103278904
2017-01-01	69.5765478314030