Year	Percent of Total
1960-01-01	25.6754286965128
1961-01-01	25.7132839651076
1962-01-01	25.6534004820289
1963-01-01	25.5292311662554
1964-01-01	25.4005734946194
1965-01-01	25.2915845150601
1966-01-01	25.2143838943308
1967-01-01	25.1415240352943
1968-01-01	25.0636877489996
1969-01-01	24.9581412409263
1970-01-01	24.8175394109051
1971-01-01	24.6583449672004
1972-01-01	24.4567638418591
1973-01-01	24.2215598481294
1974-01-01	23.9668262990685
1975-01-01	23.7012074927868
1976-01-01	23.4116959966332
1977-01-01	23.1209363816309
1978-01-01	22.8189416399399
1979-01-01	22.4928407742877
1980-01-01	22.1428697125312
1981-01-01	21.8334551692265
1982-01-01	21.5055032732675
1983-01-01	21.1719295281553
1984-01-01	20.8521531842703
1985-01-01	20.5557536023056
1986-01-01	20.2920811959539
1987-01-01	20.0456474114080
1988-01-01	19.8131378134857
1989-01-01	19.5835209924122
1990-01-01	19.3528806082265
1991-01-01	19.1536039377154
1992-01-01	18.9471596667521
1993-01-01	18.7385989394061
1994-01-01	18.5307575975618
1995-01-01	18.3212760089752
1996-01-01	18.0782915888684
1997-01-01	17.8429264288190
1998-01-01	17.6104686644188
1999-01-01	17.3763608601908
2000-01-01	17.1400225330616
2001-01-01	16.9012977562628
2002-01-01	16.6664624264296
2003-01-01	16.4421528385741
2004-01-01	16.2386757085793
2005-01-01	16.0624804388535
2006-01-01	15.9372380366309
2007-01-01	15.8369825272362
2008-01-01	15.7584504645790
2009-01-01	15.6909215240238
2010-01-01	15.6244877122271
2011-01-01	15.6227546582141
2012-01-01	15.5878739736488
2013-01-01	15.5412392602528
2014-01-01	15.5056964429865
2015-01-01	15.4887541686774
2016-01-01	15.4302347009579
2017-01-01	15.4085940641358