Year	Percent of Total
1960-01-01	11.5873762433012
1961-01-01	11.6573637687165
1962-01-01	11.7408568364994
1963-01-01	11.8377983132433
1964-01-01	11.9428516142556
1965-01-01	12.0560574788638
1966-01-01	12.2288815733912
1967-01-01	12.4014260542395
1968-01-01	12.5653021956587
1969-01-01	12.7098024875722
1970-01-01	12.8295825241643
1971-01-01	12.9931483084722
1972-01-01	13.1142682185102
1973-01-01	13.2094222064167
1974-01-01	13.3037451251465
1975-01-01	13.4087513980660
1976-01-01	13.5847763287724
1977-01-01	13.7859511845504
1978-01-01	13.9579145013545
1979-01-01	14.0147085214846
1980-01-01	13.9154416697643
1981-01-01	13.7551177026724
1982-01-01	13.4317113495259
1983-01-01	13.0544071863331
1984-01-01	12.7792331499722
1985-01-01	12.6898366969098
1986-01-01	12.7872447777732
1987-01-01	13.0509383500521
1988-01-01	13.4086201915823
1989-01-01	13.7509855602235
1990-01-01	14.0180178187346
1991-01-01	14.3118726185059
1992-01-01	14.5417896253114
1993-01-01	14.7290960470567
1994-01-01	14.9103111619990
1995-01-01	15.1050935229653
1996-01-01	15.3165156142967
1997-01-01	15.5174849921452
1998-01-01	15.7043540381802
1999-01-01	15.8685936688327
2000-01-01	16.0066934413941
2001-01-01	16.1387363428826
2002-01-01	16.2541745899997
2003-01-01	16.3494337589583
2004-01-01	16.4163196021089
2005-01-01	16.4557279546134
2006-01-01	16.4973375820492
2007-01-01	16.5028134655779
2008-01-01	16.5165450291031
2009-01-01	16.6070484746079
2010-01-01	16.8171350763184
2011-01-01	17.1160384580113
2012-01-01	17.5200082501736
2013-01-01	17.9980412052162
2014-01-01	18.4856162358131
2015-01-01	18.9384456827407
2016-01-01	19.3461951657190
2017-01-01	19.7181642445405