Year	Percent of Total
1960-01-01	25.7359840845648
1961-01-01	25.2684389574174
1962-01-01	24.7782264035256
1963-01-01	24.2593097065979
1964-01-01	23.7060466728725
1965-01-01	23.1250828754734
1966-01-01	22.7283867463114
1967-01-01	22.2595727984132
1968-01-01	21.7892055905155
1969-01-01	21.4270052454460
1970-01-01	21.2373381985018
1971-01-01	21.0935775240252
1972-01-01	21.1772021890386
1973-01-01	21.4181627559626
1974-01-01	21.6944064478241
1975-01-01	21.9417418459954
1976-01-01	22.3622820449747
1977-01-01	22.6842850758280
1978-01-01	22.9453082881610
1979-01-01	23.1877379375953
1980-01-01	23.4068563863097
1981-01-01	23.5855634891862
1982-01-01	23.6687967231148
1983-01-01	23.6681218743080
1984-01-01	23.6084700210273
1985-01-01	23.5077051736604
1986-01-01	23.0894750418493
1987-01-01	22.7811682177655
1988-01-01	22.4878777568756
1989-01-01	22.0914129701814
1990-01-01	21.5542169362090
1991-01-01	21.1541691835601
1992-01-01	20.5556035272943
1993-01-01	19.8572599674948
1994-01-01	19.2014335733110
1995-01-01	18.6476536657587
1996-01-01	18.1172534459455
1997-01-01	17.6332021194760
1998-01-01	17.1999425000542
1999-01-01	16.7987642923570
2000-01-01	16.4225916007959
2001-01-01	15.9142394601451
2002-01-01	15.5504656014047
2003-01-01	15.2694863123637
2004-01-01	15.0017832839301
2005-01-01	14.7317320350129
2006-01-01	14.6110984660751
2007-01-01	14.4463725787629
2008-01-01	14.2953899511061
2009-01-01	14.2232673411307
2010-01-01	14.2418020923122
2011-01-01	14.3817673198681
2012-01-01	14.5396677263241
2013-01-01	14.7213912602231
2014-01-01	14.9219712250553
2015-01-01	15.1307243599017
2016-01-01	15.2213369834003
2017-01-01	15.3740856707517