Year	Percent
1960-01-01	54.6268971057393
1961-01-01	54.3953108895904
1962-01-01	53.3696101714080
1963-01-01	52.0169499133383
1964-01-01	51.1397712669582
1965-01-01	50.6709241882914
1966-01-01	50.9059188769114
1967-01-01	51.1572631430965
1968-01-01	50.6986088914308
1969-01-01	50.1420644513456
1970-01-01	49.8977982902086
1971-01-01	48.8624991005161
1972-01-01	47.8249711615753
1973-01-01	48.3505736666589
1974-01-01	46.7036735294322
1975-01-01	45.8955205387038
1976-01-01	45.9265095710356
1977-01-01	46.8020824476559
1978-01-01	47.4914703321680
1979-01-01	47.7461290724207
1980-01-01	47.7512739105416
1981-01-01	47.8113761582914
1982-01-01	48.2018223954864
1983-01-01	49.1523901921938
1984-01-01	49.0677013472089
1985-01-01	48.9166657104350
1986-01-01	48.8666125789092
1987-01-01	48.8605247827493
1988-01-01	49.0988811016013
1989-01-01	49.6927453348171
1990-01-01	50.2962895649970
1991-01-01	50.8668372588055
1992-01-01	50.8463840646596
1993-01-01	50.3902599552752
1994-01-01	50.2343057113281
1995-01-01	50.0282979436041
1996-01-01	50.0613323053891
1997-01-01	50.3964569281162
1998-01-01	50.1787746429038
1999-01-01	49.6872755641358
2000-01-01	49.3555418646211
2001-01-01	49.2167344982396
2002-01-01	48.5600061780147
2003-01-01	48.3737656363936
2004-01-01	48.2997421671010
2005-01-01	48.4166214011432
2006-01-01	48.4907333994778
2007-01-01	48.4716542708735
2008-01-01	48.4078049614069
2009-01-01	48.5189242438959
2010-01-01	48.4545564654353
2011-01-01	48.1773975561127
2012-01-01	48.1930817827368
2013-01-01	48.9146496383363
2014-01-01	49.3070847684631
2015-01-01	49.6530862663355
2016-01-01	50.3656660841662
2017-01-01	51.1635827903087