Year	Percent of Total
1960-01-01	30.1905972638482
1961-01-01	30.2637094864419
1962-01-01	30.1724264519853
1963-01-01	29.9790532087051
1964-01-01	29.7776173569715
1965-01-01	29.6176652002809
1966-01-01	29.5011590635800
1967-01-01	29.4073061839227
1968-01-01	29.3459801793497
1969-01-01	29.2762744364791
1970-01-01	29.1446710624004
1971-01-01	28.8638007018717
1972-01-01	28.5842414667149
1973-01-01	28.2881365709760
1974-01-01	27.9400423713926
1975-01-01	27.5189596626643
1976-01-01	27.2224339305175
1977-01-01	26.7479056943280
1978-01-01	26.1924030095676
1979-01-01	25.6859727765210
1980-01-01	25.2890857426599
1981-01-01	24.7674123802591
1982-01-01	24.4391271495735
1983-01-01	24.2154113444805
1984-01-01	23.9601712741879
1985-01-01	23.6182092626006
1986-01-01	23.4033255257484
1987-01-01	23.0555089885010
1988-01-01	22.6543872822332
1989-01-01	22.3173498510686
1990-01-01	22.0890017980298
1991-01-01	21.8825820521850
1992-01-01	21.7828567258693
1993-01-01	21.7424145068950
1994-01-01	21.6825422193482
1995-01-01	21.5676518718001
1996-01-01	21.4738815823500
1997-01-01	21.3355041275558
1998-01-01	21.1703320297379
1999-01-01	21.0109598585929
2000-01-01	20.8667996060178
2001-01-01	20.6401597879818
2002-01-01	20.4191168137966
2003-01-01	20.2032220993156
2004-01-01	19.9924415100558
2005-01-01	19.7973674758953
2006-01-01	19.5749252707571
2007-01-01	19.3885145625098
2008-01-01	19.2471797929136
2009-01-01	19.1310609852137
2010-01-01	19.0159983262255
2011-01-01	19.0149253558717
2012-01-01	18.9565096149747
2013-01-01	18.8807186158155
2014-01-01	18.8348350656120
2015-01-01	18.8352673470043
2016-01-01	18.8983035953804
2017-01-01	19.0125412664356