Year	Percent of Total
1960-01-01	30.4066666817000
1961-01-01	30.0544365168060
1962-01-01	29.4387835735483
1963-01-01	28.6477968942812
1964-01-01	27.8579213091884
1965-01-01	27.1611553478770
1966-01-01	26.5947482217757
1967-01-01	26.0703787775767
1968-01-01	25.5833665649113
1969-01-01	25.1030583784120
1970-01-01	24.6155443865470
1971-01-01	24.0595716921056
1972-01-01	23.5024849650798
1973-01-01	22.9600492443946
1974-01-01	22.4555783534403
1975-01-01	22.0015516824480
1976-01-01	21.5270580218936
1977-01-01	21.1760143183007
1978-01-01	20.8913063032391
1979-01-01	20.6050285611290
1980-01-01	20.2965263041161
1981-01-01	20.1602016544094
1982-01-01	19.9307770263283
1983-01-01	19.6779303431507
1984-01-01	19.4919442805578
1985-01-01	19.4014725465363
1986-01-01	19.2857248616272
1987-01-01	19.2576661727694
1988-01-01	19.2823871058903
1989-01-01	19.3060437623000
1990-01-01	19.3066080730600
1991-01-01	19.2503274973227
1992-01-01	19.2242897565375
1993-01-01	19.1979792534745
1994-01-01	19.1347153095183
1995-01-01	19.0144764461062
1996-01-01	18.9580490790404
1997-01-01	18.7788567215853
1998-01-01	18.5328456722206
1999-01-01	18.3051303283702
2000-01-01	18.1359549448588
2001-01-01	17.8789492275615
2002-01-01	17.7242065741316
2003-01-01	17.6237200606148
2004-01-01	17.5044947860482
2005-01-01	17.3392975411144
2006-01-01	17.1976307277781
2007-01-01	17.0214725744402
2008-01-01	16.8298964905744
2009-01-01	16.6579443968401
2010-01-01	16.5225870152757
2011-01-01	16.4795345987432
2012-01-01	16.4282705644580
2013-01-01	16.3886137994664
2014-01-01	16.3757022570950
2015-01-01	16.3905613424089
2016-01-01	16.3703868996782
2017-01-01	16.4065562349284