Year	Percent of Total
1960-01-01	40.5933471595697
1961-01-01	40.8863480465562
1962-01-01	40.8264932186489
1963-01-01	40.5436470375690
1964-01-01	40.1744201557392
1965-01-01	39.7402508817891
1966-01-01	39.5506807578574
1967-01-01	39.0640654840568
1968-01-01	38.3509293061833
1969-01-01	37.5104942116138
1970-01-01	36.6019108148693
1971-01-01	35.5169307758158
1972-01-01	34.5487545744304
1973-01-01	33.6012281507675
1974-01-01	32.5304607576147
1975-01-01	31.2935404657505
1976-01-01	30.2132753367037
1977-01-01	28.8883537019408
1978-01-01	27.4935715966051
1979-01-01	26.2533094468526
1980-01-01	25.2572949833658
1981-01-01	24.6278847793282
1982-01-01	24.2014883193886
1983-01-01	23.9335274209902
1984-01-01	23.7072619115314
1985-01-01	23.4468832749865
1986-01-01	22.8987023176441
1987-01-01	22.3304256776710
1988-01-01	21.7717339511214
1989-01-01	21.2499918848558
1990-01-01	20.7594484368046
1991-01-01	20.2879423746278
1992-01-01	19.8837732031668
1993-01-01	19.5020352293989
1994-01-01	19.0923960452420
1995-01-01	18.6438789850525
1996-01-01	18.3678772663698
1997-01-01	17.9710751407621
1998-01-01	17.5555111374462
1999-01-01	17.1932821080546
2000-01-01	16.8723496147909
2001-01-01	16.2971754037975
2002-01-01	15.7802858232965
2003-01-01	15.2973112998006
2004-01-01	14.8222068718755
2005-01-01	14.3521573177503
2006-01-01	13.7433720833960
2007-01-01	13.2143308075775
2008-01-01	12.7425625579674
2009-01-01	12.3137978872941
2010-01-01	11.9350409047630
2011-01-01	11.6529657229916
2012-01-01	11.3598462456161
2013-01-01	11.1313435930062
2014-01-01	11.0606161903093
2015-01-01	11.1788355605620
2016-01-01	11.2119896319830
2017-01-01	11.4888994163247