Year	Percent
1968-01-01	52.4513017856967
1969-01-01	51.9441351189849
1970-01-01	52.5178256661484
1971-01-01	51.8917856587799
1972-01-01	49.7678697319342
1973-01-01	49.2002278240588
1974-01-01	46.0844178171149
1975-01-01	44.5319861787022
1976-01-01	43.1010571323964
1977-01-01	43.4550682603412
1978-01-01	43.1850118993148
1979-01-01	42.8624901488500
1980-01-01	42.5726140561233
1981-01-01	42.2872124188461
1982-01-01	41.6661967841475
1983-01-01	42.5500233388398
1984-01-01	42.2110595842074
1985-01-01	41.3646419189617
1986-01-01	41.6200580904488
1987-01-01	41.0637611604280
1988-01-01	41.2949803213193
1989-01-01	42.2960877517592
1990-01-01	43.0973585034717
1991-01-01	44.0220342551068
1992-01-01	44.6253065723156
1993-01-01	44.3018395613320
1994-01-01	44.7350309080932
1995-01-01	44.4827193862753
1996-01-01	44.5381674773494
1997-01-01	44.5753638583991
1998-01-01	44.3267143661712
1999-01-01	43.0449390816770
2000-01-01	43.1059173693013
2001-01-01	42.4735845989068
2002-01-01	41.0706963574780
2003-01-01	40.6533650728725
2004-01-01	40.7982777900309
2005-01-01	41.7435636729869
2006-01-01	42.0413049818863
2007-01-01	41.4880820762537
2008-01-01	41.6383853124520
2009-01-01	40.8710404576585
2010-01-01	40.1030077088838
2011-01-01	40.2855995381344
2012-01-01	38.8971310740742
2013-01-01	40.5554518246774
2014-01-01	40.8504240726829
2015-01-01	40.6883454341235
2016-01-01	42.5818701515062
2017-01-01	43.0151122429088