Year	Percent of Total
1960-01-01	47.0007964442617
1961-01-01	47.1003695726687
1962-01-01	47.3111987148997
1963-01-01	47.5258808087227
1964-01-01	47.5964289943329
1965-01-01	47.4680785521532
1966-01-01	47.3795689993615
1967-01-01	47.1190207672747
1968-01-01	46.7457921317493
1969-01-01	46.3556427079681
1970-01-01	45.9972061232470
1971-01-01	45.6783883120849
1972-01-01	45.3732010736868
1973-01-01	45.0782248651043
1974-01-01	44.7777894479150
1975-01-01	44.4652787578504
1976-01-01	44.1956140987372
1977-01-01	43.9287210019681
1978-01-01	43.6609276638601
1979-01-01	43.3887456508594
1980-01-01	43.1114834180954
1981-01-01	42.8791176344526
1982-01-01	42.6226429463335
1983-01-01	42.3564824066870
1984-01-01	42.0999639633669
1985-01-01	41.8617707706228
1986-01-01	41.6709913212068
1987-01-01	41.5031440078553
1988-01-01	41.3413616283604
1989-01-01	41.1582423838627
1990-01-01	40.9391730538650
1991-01-01	40.7675708207626
1992-01-01	40.5438078480121
1993-01-01	40.2860547538556
1994-01-01	40.0219868536113
1995-01-01	39.7633359950564
1996-01-01	39.5016848153812
1997-01-01	39.2608070286794
1998-01-01	39.0219870632990
1999-01-01	38.7640364656106
2000-01-01	38.4827544628574
2001-01-01	38.2329599776264
2002-01-01	37.9694798140330
2003-01-01	37.6972460505988
2004-01-01	37.4084149088482
2005-01-01	37.0750088464996
2006-01-01	36.5542835444567
2007-01-01	35.9800048133408
2008-01-01	35.3254220761791
2009-01-01	34.6132929398775
2010-01-01	33.9014429880671
2011-01-01	33.5400114654032
2012-01-01	33.1735666030417
2013-01-01	32.8311049786724
2014-01-01	32.5199267001484
2015-01-01	32.2291805588519
2016-01-01	31.9649893899763
2017-01-01	31.7157536893781