Year	Percent of Total
1960-01-01	28.8137241617857
1961-01-01	29.4586903274411
1962-01-01	29.8858929171788
1963-01-01	30.1347255308238
1964-01-01	30.2809446014278
1965-01-01	30.3535270189932
1966-01-01	30.1470882342129
1967-01-01	29.8836552423265
1968-01-01	29.5353382909527
1969-01-01	29.0801894133178
1970-01-01	28.5314435120414
1971-01-01	27.7711132358098
1972-01-01	27.0792539034251
1973-01-01	26.4397902624984
1974-01-01	25.8243829516168
1975-01-01	25.2140318376551
1976-01-01	24.7371448625290
1977-01-01	24.1644367082033
1978-01-01	23.5721667943828
1979-01-01	23.0846170864457
1980-01-01	22.7689485283616
1981-01-01	22.5785328102538
1982-01-01	22.5644244138069
1983-01-01	22.6635438943857
1984-01-01	22.7670614566442
1985-01-01	22.8195048962719
1986-01-01	22.9604824214552
1987-01-01	23.0356573609048
1988-01-01	23.0445136869062
1989-01-01	23.0055208170279
1990-01-01	22.9210854308659
1991-01-01	22.8268283173909
1992-01-01	22.6422560337568
1993-01-01	22.3763125569212
1994-01-01	22.0476922313239
1995-01-01	21.6670702565925
1996-01-01	21.0455222793942
1997-01-01	20.4644149380213
1998-01-01	19.8774232509899
1999-01-01	19.2344136082619
2000-01-01	18.5302642775652
2001-01-01	17.9077988862713
2002-01-01	17.2558093436491
2003-01-01	16.6131522474105
2004-01-01	16.0475842371867
2005-01-01	15.5981010530224
2006-01-01	15.2884013157957
2007-01-01	15.0482590503545
2008-01-01	14.8934227702812
2009-01-01	14.8255805066687
2010-01-01	14.8455131392977
2011-01-01	14.9907060252416
2012-01-01	15.2123952012990
2013-01-01	15.5000547531771
2014-01-01	15.8191309489205
2015-01-01	16.1359349560584
2016-01-01	16.4539355416358
2017-01-01	16.7416499073016