Year	Percent of Total
1960-01-01	22.4325072371786
1961-01-01	22.1783779168124
1962-01-01	21.8351683988239
1963-01-01	21.4641974658312
1964-01-01	21.1502290310704
1965-01-01	20.9340105114171
1966-01-01	20.8329246213962
1967-01-01	20.7890342026639
1968-01-01	20.8002269361529
1969-01-01	20.8278704040954
1970-01-01	20.8381564748782
1971-01-01	20.8539916966750
1972-01-01	20.8602424943713
1973-01-01	20.8431034013208
1974-01-01	20.7888017178438
1975-01-01	20.6899189249195
1976-01-01	20.5430602916195
1977-01-01	20.3462738593537
1978-01-01	20.1120180771434
1979-01-01	19.8570771600926
1980-01-01	19.5893432902799
1981-01-01	19.2610936073095
1982-01-01	18.9532890925844
1983-01-01	18.6612737704896
1984-01-01	18.3893775388349
1985-01-01	18.1547042159688
1986-01-01	18.0068930322986
1987-01-01	17.9043459632616
1988-01-01	17.8556294446629
1989-01-01	17.8636857036346
1990-01-01	17.9249231737483
1991-01-01	18.1172194714125
1992-01-01	18.3198917706508
1993-01-01	18.5304162356507
1994-01-01	18.7174153358504
1995-01-01	18.8413973079596
1996-01-01	18.9082840634094
1997-01-01	18.8532835080252
1998-01-01	18.7114016608108
1999-01-01	18.5528620211651
2000-01-01	18.4222958822920
2001-01-01	18.0866311454987
2002-01-01	17.9103890347545
2003-01-01	17.8050370097622
2004-01-01	17.6499134266207
2005-01-01	17.4045758961293
2006-01-01	17.3440986321417
2007-01-01	17.1189719622190
2008-01-01	16.8222962490622
2009-01-01	16.5957765724040
2010-01-01	16.5079261627694
2011-01-01	16.5123265720758
2012-01-01	16.6236711038060
2013-01-01	16.8300408715450
2014-01-01	17.0705523245253
2015-01-01	17.2970733538416
2016-01-01	17.3995960166029
2017-01-01	17.5349453081069