Year	Percent of Total
1960-01-01	40.2762276460953
1961-01-01	40.5591773927033
1962-01-01	40.9281028431164
1963-01-01	41.3180935392923
1964-01-01	41.6183622188676
1965-01-01	41.7767135792774
1966-01-01	42.0252833974835
1967-01-01	42.1114242846185
1968-01-01	42.0805807552058
1969-01-01	41.9954272936224
1970-01-01	41.8816932780194
1971-01-01	41.8312155563507
1972-01-01	41.7343988385255
1973-01-01	41.6023119518241
1974-01-01	41.4479835750951
1975-01-01	41.2871323917775
1976-01-01	41.1847479451610
1977-01-01	41.1147861645005
1978-01-01	41.0711654917697
1979-01-01	41.0550088695007
1980-01-01	41.0755732807204
1981-01-01	41.2806979463180
1982-01-01	41.5038654018367
1983-01-01	41.7433749318483
1984-01-01	41.9813923272315
1985-01-01	42.1961891828179
1986-01-01	42.5385018528411
1987-01-01	42.7640194957911
1988-01-01	42.9128968606917
1989-01-01	43.0285784109368
1990-01-01	43.1198107196159
1991-01-01	43.0919026737615
1992-01-01	43.0790276127914
1993-01-01	43.0284946761293
1994-01-01	42.8727707721953
1995-01-01	42.5899824113284
1996-01-01	42.2734868501911
1997-01-01	41.8519663148853
1998-01-01	41.3568206170552
1999-01-01	40.8405337300780
2000-01-01	40.3318322182192
2001-01-01	39.8727901665872
2002-01-01	39.3978403195660
2003-01-01	38.9206902605811
2004-01-01	38.4531039968734
2005-01-01	38.0007500482544
2006-01-01	37.5480540481773
2007-01-01	37.1289234394163
2008-01-01	36.7271442465551
2009-01-01	36.3162307023233
2010-01-01	35.8830643213635
2011-01-01	35.4844045186945
2012-01-01	35.0497365686967
2013-01-01	34.5976466519220
2014-01-01	34.1571777104793
2015-01-01	33.7413632505687
2016-01-01	33.3402198180677
2017-01-01	32.9725024403006