Year	Percent of Total
1960-01-01	11.7592374677967
1961-01-01	11.9379069374295
1962-01-01	12.1214196169015
1963-01-01	12.3086980638167
1964-01-01	12.4956125686735
1965-01-01	12.6818547594250
1966-01-01	12.8898695698831
1967-01-01	13.0905557924948
1968-01-01	13.2877639561831
1969-01-01	13.4892670855416
1970-01-01	13.7008132673264
1971-01-01	13.9955406468520
1972-01-01	14.2877463044944
1973-01-01	14.5770436667755
1974-01-01	14.8609463604457
1975-01-01	15.1381179748553
1976-01-01	15.4118037773148
1977-01-01	15.6700859745755
1978-01-01	15.9108267388825
1979-01-01	16.1284158571991
1980-01-01	16.3212702514015
1981-01-01	16.5609532072155
1982-01-01	16.7580355186583
1983-01-01	16.9297767773509
1984-01-01	17.0978149833822
1985-01-01	17.2719203910381
1986-01-01	17.4295756380837
1987-01-01	17.5791017183593
1988-01-01	17.7066475506117
1989-01-01	17.7914769738952
1990-01-01	17.8237370940768
1991-01-01	17.8238444212538
1992-01-01	17.7803797006425
1993-01-01	17.7023396963636
1994-01-01	17.6063855541919
1995-01-01	17.5084140409804
1996-01-01	17.4642921684384
1997-01-01	17.4271238907669
1998-01-01	17.3938049665601
1999-01-01	17.3536419064363
2000-01-01	17.3036849050401
2001-01-01	17.3040663004860
2002-01-01	17.2625582718116
2003-01-01	17.2186273867996
2004-01-01	17.2246043913008
2005-01-01	17.3066074334553
2006-01-01	17.3959550866158
2007-01-01	17.5486888211957
2008-01-01	17.7485603920800
2009-01-01	17.9741230934351
2010-01-01	18.2185664835816
2011-01-01	18.4993025485607
2012-01-01	18.8066082186945
2013-01-01	19.1161079897376
2014-01-01	19.3884828083872
2015-01-01	19.5977493876468
2016-01-01	19.8338343566421
2017-01-01	19.9851049890416