Year	Percent of Total
1960-01-01	49.5275184584626
1961-01-01	49.1032839350972
1962-01-01	48.6090229727807
1963-01-01	48.1479730650378
1964-01-01	47.8614843348584
1965-01-01	47.7974598451519
1966-01-01	47.7292740137930
1967-01-01	47.8650201804307
1968-01-01	48.1250905513270
1969-01-01	48.3905810803238
1970-01-01	48.5989146436500
1971-01-01	48.6253010832529
1972-01-01	48.6137125686070
1973-01-01	48.5808949351158
1974-01-01	48.5603741334311
1975-01-01	48.5663203247894
1976-01-01	48.4041001393004
1977-01-01	48.2878984061953
1978-01-01	48.2052723363920
1979-01-01	48.1387344084937
1980-01-01	48.0830440900195
1981-01-01	48.0814075575193
1982-01-01	48.1086735486032
1983-01-01	48.1722075005280
1984-01-01	48.2873927832268
1985-01-01	48.4637932834941
1986-01-01	48.6199541414462
1987-01-01	48.8392683928987
1988-01-01	49.1236378719781
1989-01-01	49.4770722003264
1990-01-01	49.9008570587693
1991-01-01	50.4198484629877
1992-01-01	51.0132375729739
1993-01-01	51.6543773016065
1994-01-01	52.2982828946034
1995-01-01	52.9152363683309
1996-01-01	53.5334049099421
1997-01-01	54.0627296168739
1998-01-01	54.5518102884143
1999-01-01	55.0702755703451
2000-01-01	55.6452780502263
2001-01-01	55.9275093146324
2002-01-01	56.3444743740030
2003-01-01	56.8162266370206
2004-01-01	57.2275574985014
2005-01-01	57.5250274520732
2006-01-01	58.1677947586191
2007-01-01	58.6544175091426
2008-01-01	59.0631013552817
2009-01-01	59.5366276311720
2010-01-01	60.1641936940936
2011-01-01	59.5780443369589
2012-01-01	59.0725068644803
2013-01-01	58.6602316576978
2014-01-01	58.2760066218510
2015-01-01	57.8680945975570
2016-01-01	58.4570818742220
2017-01-01	59.0799178187823