Year	Percent of Total
1960-01-01	30.7256169348043
1961-01-01	30.6601889545865
1962-01-01	30.5689882064191
1963-01-01	30.4494483355718
1964-01-01	30.2987907084878
1965-01-01	30.1187072523525
1966-01-01	29.9757200177560
1967-01-01	29.8033773728586
1968-01-01	29.6171775256716
1969-01-01	29.4415903897600
1970-01-01	29.2942769337145
1971-01-01	29.2027817441851
1972-01-01	29.1390826814033
1973-01-01	29.1055728012435
1974-01-01	29.1085193842299
1975-01-01	29.1546717637931
1976-01-01	29.3238864965537
1977-01-01	29.5682191366987
1978-01-01	29.8527946284115
1979-01-01	30.1182530289295
1980-01-01	30.3265849490327
1981-01-01	30.6243370613219
1982-01-01	30.7488859672869
1983-01-01	30.7728148863521
1984-01-01	30.7951190244787
1985-01-01	30.8555495624817
1986-01-01	30.7594352885177
1987-01-01	30.7839347251125
1988-01-01	30.8377404273691
1989-01-01	30.7963370813284
1990-01-01	30.6132108172326
1991-01-01	30.4694944417227
1992-01-01	30.1804647972015
1993-01-01	29.8066217334468
1994-01-01	29.4432899479616
1995-01-01	29.1340368318574
1996-01-01	28.8671309923110
1997-01-01	28.6248615105963
1998-01-01	28.4059970878761
1999-01-01	28.1951916264726
2000-01-01	27.9848247526570
2001-01-01	27.7334094017938
2002-01-01	27.5273355033351
2003-01-01	27.3412445552824
2004-01-01	27.1428296991977
2005-01-01	26.9188929257952
2006-01-01	26.7437205644547
2007-01-01	26.5193585104752
2008-01-01	26.2745475509138
2009-01-01	26.0530036625287
2010-01-01	25.8737791575171
2011-01-01	25.6997553753367
2012-01-01	25.5716149414804
2013-01-01	25.4668972735613
2014-01-01	25.3478919949657
2015-01-01	25.1959376536309
2016-01-01	25.0586568015503
2017-01-01	24.8853149850260