Year	Percent
1968-01-01	44.8477066922299
1969-01-01	44.6331360970669
1970-01-01	44.2562894447563
1971-01-01	44.6608357410375
1972-01-01	43.2503242061304
1973-01-01	44.0581177890815
1974-01-01	43.2665892232680
1975-01-01	43.0941459446622
1976-01-01	43.6834982936747
1977-01-01	44.0724994082754
1978-01-01	44.8150736302235
1979-01-01	45.0029321722084
1980-01-01	44.8937973264031
1981-01-01	44.1355926574092
1982-01-01	44.4437018658290
1983-01-01	45.3647570427985
1984-01-01	44.2694003160851
1985-01-01	44.6116912122364
1986-01-01	43.8682685176198
1987-01-01	44.2172843368264
1988-01-01	44.4095177539039
1989-01-01	45.3361395633071
1990-01-01	46.6071628503302
1991-01-01	47.9366198786572
1992-01-01	47.9169219025019
1993-01-01	47.9593924636676
1994-01-01	47.2190481651286
1995-01-01	47.5629707670964
1996-01-01	47.5448177567716
1997-01-01	48.3266022641788
1998-01-01	48.4792796199179
1999-01-01	48.3869202550117
2000-01-01	47.9313940069397
2001-01-01	47.2646314749654
2002-01-01	47.1036284843165
2003-01-01	47.5507438856424
2004-01-01	48.6224946309984
2005-01-01	49.4018328581789
2006-01-01	50.0345503437847
2007-01-01	51.3253555601382
2008-01-01	51.8744781775885
2009-01-01	51.8201120153813
2010-01-01	52.2371432464056
2011-01-01	52.7474513198399
2012-01-01	52.4817798731889
2013-01-01	54.3099514587672
2014-01-01	56.1291527568974
2015-01-01	57.9767675121264
2016-01-01	59.7289932773879
2017-01-01	61.9915329457067