Year	Percent of Total
1960-01-01	11.4739927071827
1961-01-01	11.6860545269638
1962-01-01	11.8797757128146
1963-01-01	12.0652188723324
1964-01-01	12.2577628992628
1965-01-01	12.4660790297137
1966-01-01	12.6978145286985
1967-01-01	12.9304147283257
1968-01-01	13.1610883072749
1969-01-01	13.3857862920462
1970-01-01	13.6054868426532
1971-01-01	13.8922289940443
1972-01-01	14.1648329610917
1973-01-01	14.4206473674012
1974-01-01	14.6522926175048
1975-01-01	14.8527807079756
1976-01-01	15.1603025673265
1977-01-01	15.4197576749228
1978-01-01	15.6100757773535
1979-01-01	15.6935566301779
1980-01-01	15.6479812108839
1981-01-01	15.5297671057551
1982-01-01	15.2900112140831
1983-01-01	14.9924823319374
1984-01-01	14.7305100194151
1985-01-01	14.5632657363571
1986-01-01	14.5314122370323
1987-01-01	14.5849930265022
1988-01-01	14.6913284611815
1989-01-01	14.8036876040216
1990-01-01	14.8962390837238
1991-01-01	15.0410835471830
1992-01-01	15.1756979413765
1993-01-01	15.2947709148058
1994-01-01	15.3892818455159
1995-01-01	15.4587169243596
1996-01-01	15.6649795016568
1997-01-01	15.8182701797326
1998-01-01	15.9649455347015
1999-01-01	16.1712645056654
2000-01-01	16.4728782509009
2001-01-01	16.8849485688798
2002-01-01	17.3818065284329
2003-01-01	17.9188114265400
2004-01-01	18.4243475292783
2005-01-01	18.8570457990141
2006-01-01	19.3116995703955
2007-01-01	19.6936393588564
2008-01-01	20.0129176359639
2009-01-01	20.2904969087370
2010-01-01	20.5416059885690
2011-01-01	20.6824241190165
2012-01-01	20.7858986605372
2013-01-01	20.8766405973907
2014-01-01	20.9819577109538
2015-01-01	21.1175632227669
2016-01-01	21.2696084530498
2017-01-01	21.4532222821712