Year	Percent of Total
1960-01-01	50.1122725600229
1961-01-01	49.6914335664336
1962-01-01	49.2027826278702
1963-01-01	48.7362561033963
1964-01-01	48.4334847229361
1965-01-01	48.3515220858807
1966-01-01	48.3719956334343
1967-01-01	48.5232080997971
1968-01-01	48.7835776783048
1969-01-01	49.1020957904923
1970-01-01	49.4392217826142
1971-01-01	49.6183051746786
1972-01-01	49.8341421631878
1973-01-01	50.0545920239741
1974-01-01	50.2468796186217
1975-01-01	50.3999648162543
1976-01-01	50.3850867931855
1977-01-01	50.3739988418881
1978-01-01	50.3583713117640
1979-01-01	50.3386853869774
1980-01-01	50.3243166733848
1981-01-01	50.2440115967211
1982-01-01	50.1585638294002
1983-01-01	50.0903785467946
1984-01-01	50.0734267540844
1985-01-01	50.1275110262865
1986-01-01	50.1942760402716
1987-01-01	50.3409656026370
1988-01-01	50.5480723727678
1989-01-01	50.7889373444152
1990-01-01	51.0536570182878
1991-01-01	51.4473537935815
1992-01-01	51.8612640105909
1993-01-01	52.3038779373693
1994-01-01	52.7927710710119
1995-01-01	53.3361750546591
1996-01-01	53.9308697558426
1997-01-01	54.5567663329601
1998-01-01	55.2067037591799
1999-01-01	55.8678777936262
2000-01-01	56.5320733127026
2001-01-01	57.2144880654806
2002-01-01	57.8922272491199
2003-01-01	58.5537082615340
2004-01-01	59.1816717432218
2005-01-01	59.7659967936515
2006-01-01	60.3951663522752
2007-01-01	60.9556933532243
2008-01-01	61.4692342809178
2009-01-01	61.9705074364948
2010-01-01	62.4766305379329
2011-01-01	62.9962533274103
2012-01-01	63.5359431883845
2013-01-01	64.0597724726598
2014-01-01	64.5157954019598
2015-01-01	64.8803895406718
2016-01-01	65.2453817345504
2017-01-01	65.5221057835837