Year	Percent of Total
1960-01-01	28.8749630048750
1961-01-01	28.7255270204229
1962-01-01	28.3611893517899
1963-01-01	27.8477191268933
1964-01-01	27.3462648125293
1965-01-01	26.9704360798961
1966-01-01	26.4327063887760
1967-01-01	26.2612991993926
1968-01-01	26.2758414335597
1969-01-01	26.2077752075689
1970-01-01	25.9421922650792
1971-01-01	26.1649198210063
1972-01-01	25.9244038465419
1973-01-01	25.4905911262909
1974-01-01	25.2461071389030
1975-01-01	25.3477637381914
1976-01-01	25.2980495581697
1977-01-01	25.6876338256314
1978-01-01	26.2832447548631
1979-01-01	26.7111221049880
1980-01-01	26.7960364888138
1981-01-01	26.8689013636301
1982-01-01	26.5800093747057
1983-01-01	26.0530705211867
1984-01-01	25.5390991267997
1985-01-01	25.1747970861396
1986-01-01	24.7416860106788
1987-01-01	24.5234668339848
1988-01-01	24.4075017102819
1989-01-01	24.1854655864219
1990-01-01	23.7492631242222
1991-01-01	23.4789928785929
1992-01-01	22.8858557679217
1993-01-01	22.1031480269926
1994-01-01	21.3677608860462
1995-01-01	20.8046980482698
1996-01-01	20.0685883477865
1997-01-01	19.6404952899121
1998-01-01	19.3774649539228
1999-01-01	19.0419784012577
2000-01-01	18.5310027129272
2001-01-01	18.1498066673990
2002-01-01	17.5661812602484
2003-01-01	16.8837943571882
2004-01-01	16.3003578686170
2005-01-01	15.9173819927733
2006-01-01	15.6535031525723
2007-01-01	15.5905908653933
2008-01-01	15.6614516323934
2009-01-01	15.7445197644480
2010-01-01	15.7781470148232
2011-01-01	15.7541674413603
2012-01-01	15.6775322110598
2013-01-01	15.5675688119727
2014-01-01	15.4726773537687
2015-01-01	15.4167099126154
2016-01-01	15.3127378421862
2017-01-01	15.2638157056961