Year	Percent of Total
1960-01-01	26.0935828622698
1961-01-01	25.8407182457567
1962-01-01	25.4818712400555
1963-01-01	25.0550021012039
1964-01-01	24.6308466996056
1965-01-01	24.2449288352527
1966-01-01	23.9190472138077
1967-01-01	23.6198800319343
1968-01-01	23.3478679972986
1969-01-01	23.0943375605491
1970-01-01	22.8570965113507
1971-01-01	22.6933434030832
1972-01-01	22.5483646548787
1973-01-01	22.4289523842973
1974-01-01	22.3370956596969
1975-01-01	22.2676311953695
1976-01-01	22.2653429139924
1977-01-01	22.2613337938407
1978-01-01	22.2475745960530
1979-01-01	22.2127353686305
1980-01-01	22.1506345188385
1981-01-01	22.1217600896748
1982-01-01	22.0399564601585
1983-01-01	21.9201248643762
1984-01-01	21.7873160188992
1985-01-01	21.6505626391389
1986-01-01	21.3939663653338
1987-01-01	21.1931134877716
1988-01-01	20.9951103092612
1989-01-01	20.7252171016267
1990-01-01	20.3469348814794
1991-01-01	20.0243872114285
1992-01-01	19.5595259376668
1993-01-01	18.9980653900721
1994-01-01	18.4302301364218
1995-01-01	17.9095329137219
1996-01-01	17.3827695362398
1997-01-01	16.9187573964353
1998-01-01	16.5019408756724
1999-01-01	16.0889156319733
2000-01-01	15.6602570185978
2001-01-01	15.1743902626629
2002-01-01	14.7237393539811
2003-01-01	14.3020376656179
2004-01-01	13.9172705463742
2005-01-01	13.5840342811198
2006-01-01	13.4559412057167
2007-01-01	13.3358504200306
2008-01-01	13.2509738918298
2009-01-01	13.2255771503065
2010-01-01	13.2622467955687
2011-01-01	13.3769780728209
2012-01-01	13.5052978756380
2013-01-01	13.6552538685941
2014-01-01	13.8252416698917
2015-01-01	14.0065004076687
2016-01-01	14.0930357650164
2017-01-01	14.2365853909856