Year	Percent of Total
1960-01-01	58.9851702693382
1961-01-01	58.2024905251760
1962-01-01	57.4690850871095
1963-01-01	56.7623790785375
1964-01-01	56.0580358033808
1965-01-01	55.3947803748321
1966-01-01	54.4167696549102
1967-01-01	53.4778403913035
1968-01-01	52.6214316245146
1969-01-01	51.9054424727699
1970-01-01	51.3656623592012
1971-01-01	51.1543165407361
1972-01-01	51.1402208342447
1973-01-01	51.2790415600473
1974-01-01	51.5125382956995
1975-01-01	51.8037782286715
1976-01-01	51.7584331567910
1977-01-01	51.8267742648685
1978-01-01	51.9430191010934
1979-01-01	52.0321280951325
1980-01-01	52.0352306089592
1981-01-01	51.9504681733614
1982-01-01	51.7351141445046
1983-01-01	51.4640840118851
1984-01-01	51.2333768782146
1985-01-01	51.0781123936784
1986-01-01	50.5339763797573
1987-01-01	50.1920009452354
1988-01-01	49.9792743645329
1989-01-01	49.8155543756781
1990-01-01	49.6875209999328
1991-01-01	49.6374383035769
1992-01-01	49.6380033024260
1993-01-01	49.7370689477396
1994-01-01	50.0078491987780
1995-01-01	50.4880314229264
1996-01-01	51.2511230994073
1997-01-01	52.1668716299309
1998-01-01	53.2205820078305
1999-01-01	54.3707465644628
2000-01-01	55.5780643688655
2001-01-01	57.3893745187735
2002-01-01	59.1905307109781
2003-01-01	60.9409382248709
2004-01-01	62.6068300351456
2005-01-01	64.1574351704325
2006-01-01	65.5494836133928
2007-01-01	66.8807093760229
2008-01-01	68.0971673998852
2009-01-01	69.1617230981013
2010-01-01	70.0560476912905
2011-01-01	70.8176610304133
2012-01-01	71.4246134804753
2013-01-01	71.8747247714502
2014-01-01	72.2148601214461
2015-01-01	72.4870519570844
2016-01-01	72.4642085675011
2017-01-01	72.4706071092980