Year	Percent of Total
1960-01-01	53.8277761714076
1961-01-01	53.6127737514131
1962-01-01	53.4916958868520
1963-01-01	53.4339524588114
1964-01-01	53.3793642036180
1965-01-01	53.2605069558652
1966-01-01	52.9991336105554
1967-01-01	52.7959914672623
1968-01-01	52.6170995693244
1969-01-01	52.4740442683621
1970-01-01	52.4048438163252
1971-01-01	52.0930958217693
1972-01-01	51.8318797712386
1973-01-01	51.6342536615227
1974-01-01	51.5009619701420
1975-01-01	51.4250059947412
1976-01-01	51.1498485466361
1977-01-01	50.9616186353663
1978-01-01	50.8395016590535
1979-01-01	50.7532031756674
1980-01-01	50.6733400984035
1981-01-01	50.5077632280349
1982-01-01	50.4199218817001
1983-01-01	50.3865525447767
1984-01-01	50.4023103988648
1985-01-01	50.4747318931421
1986-01-01	50.4015731178768
1987-01-01	50.3928809929535
1988-01-01	50.4519074643600
1989-01-01	50.5870675593598
1990-01-01	50.8012537827375
1991-01-01	50.7889068022299
1992-01-01	50.8840072815552
1993-01-01	51.0606343141302
1994-01-01	51.2796008878765
1995-01-01	51.5148019758429
1996-01-01	51.9646503895424
1997-01-01	52.4148917941379
1998-01-01	52.8626595765825
1999-01-01	53.3135268968010
2000-01-01	53.7641586627305
2001-01-01	53.9393399937791
2002-01-01	54.1252243180579
2003-01-01	54.3133037219825
2004-01-01	54.4895040254052
2005-01-01	54.6450387347561
2006-01-01	54.6307062670270
2007-01-01	54.6428151602740
2008-01-01	54.6707972805332
2009-01-01	54.7097436020568
2010-01-01	54.7626216524434
2011-01-01	54.7657517679296
2012-01-01	54.8033801969303
2013-01-01	54.8802007341244
2014-01-01	55.0048105421076
2015-01-01	55.1804133371769
2016-01-01	55.3587031087349
2017-01-01	55.5799188837110