Year	Percent of Total
1960-01-01	11.8739245137507
1961-01-01	12.0218652683833
1962-01-01	12.1711006792667
1963-01-01	12.3209943027157
1964-01-01	12.4671449429079
1965-01-01	12.6098442609593
1966-01-01	12.8072361036271
1967-01-01	12.9951048594392
1968-01-01	13.1677015386915
1969-01-01	13.3170466301327
1970-01-01	13.4396574814839
1971-01-01	13.6292853266640
1972-01-01	13.7708161256250
1973-01-01	13.8777097801294
1974-01-01	13.9673664361005
1975-01-01	14.0473409331914
1976-01-01	14.2098794081785
1977-01-01	14.3688263342371
1978-01-01	14.4913891835304
1979-01-01	14.5247132314909
1980-01-01	14.4450574754572
1981-01-01	14.3742500449366
1982-01-01	14.1894031683476
1983-01-01	13.9632830464706
1984-01-01	13.8005935776078
1985-01-01	13.7596255482486
1986-01-01	13.9097664088040
1987-01-01	14.1619399717711
1988-01-01	14.4689939371545
1989-01-01	14.7589381189270
1990-01-01	14.9914995626862
1991-01-01	15.2508729317208
1992-01-01	15.4550147889965
1993-01-01	15.6199122533249
1994-01-01	15.7724968070344
1995-01-01	15.9289752270328
1996-01-01	16.1447257249633
1997-01-01	16.3524403721556
1998-01-01	16.5479683654839
1999-01-01	16.7210360442938
2000-01-01	16.8664893411643
2001-01-01	17.0084288051025
2002-01-01	17.1213187604108
2003-01-01	17.2065216807089
2004-01-01	17.2626889566214
2005-01-01	17.2910563364390
2006-01-01	17.3149620883789
2007-01-01	17.2947890858291
2008-01-01	17.2619643455022
2009-01-01	17.2646402628291
2010-01-01	17.3340272585350
2011-01-01	17.4343097205387
2012-01-01	17.5952109206888
2013-01-01	17.7911838322911
2014-01-01	17.9809434947943
2015-01-01	18.1423094027785
2016-01-01	18.3686069992910
2017-01-01	18.5708951071173