Year	Percent of Total
1960-01-01	46.4761216325660
1961-01-01	46.9413345825490
1962-01-01	47.4998882148048
1963-01-01	48.0396437008679
1964-01-01	48.4089874192745
1965-01-01	48.5556947459184
1966-01-01	48.6803573981776
1967-01-01	48.6039705890038
1968-01-01	48.4059934028094
1969-01-01	48.2069532605055
1970-01-01	48.0691015143434
1971-01-01	48.0788122462565
1972-01-01	48.1329137145833
1973-01-01	48.2129701239768
1974-01-01	48.2831187543568
1975-01-01	48.3277762399157
1976-01-01	48.5161255228257
1977-01-01	48.6601389044480
1978-01-01	48.7715107375854
1979-01-01	48.8674181427805
1980-01-01	48.9522296723666
1981-01-01	48.9707766827759
1982-01-01	48.9616252044920
1983-01-01	48.9141044227766
1984-01-01	48.8088126268514
1985-01-01	48.6341250218808
1986-01-01	48.4601525662034
1987-01-01	48.2192708786278
1988-01-01	47.9102311096161
1989-01-01	47.5301570041631
1990-01-01	47.0778683661023
1991-01-01	46.5265478490848
1992-01-01	45.9015468543655
1993-01-01	45.2285569766282
1994-01-01	44.5523225343174
1995-01-01	43.9028232701953
1996-01-01	43.2403140135677
1997-01-01	42.6726982440272
1998-01-01	42.1515990362904
1999-01-01	41.6077904647401
2000-01-01	41.0141755014732
2001-01-01	40.7332566385710
2002-01-01	40.3152675100353
2003-01-01	39.8396096849741
2004-01-01	39.4205969706353
2005-01-01	39.1085932354615
2006-01-01	38.4476491829728
2007-01-01	37.9434248981017
2008-01-01	37.5165549897240
2009-01-01	37.0218372790679
2010-01-01	36.3665558232203
2011-01-01	36.8516180004470
2012-01-01	37.2582263459026
2013-01-01	37.5651978043874
2014-01-01	37.8276933556006
2015-01-01	38.0916624068114
2016-01-01	37.3640409164115
2017-01-01	36.5761974853896