Year Percent of Total 1960-01-01 3.426387719411880 1961-01-01 3.170818575753380 1962-01-01 2.941176470588230 1963-01-01 2.720481659047830 1964-01-01 2.505612543222000 1965-01-01 2.279166278714040 1966-01-01 2.075011995189460 1967-01-01 1.883335388735220 1968-01-01 1.710208849634810 1969-01-01 1.558237660680990 1970-01-01 1.431428583560860 1971-01-01 1.205847751857910 1972-01-01 1.148575549945910 1973-01-01 1.208034765619100 1974-01-01 1.334213049787430 1975-01-01 1.488299261803570 1976-01-01 1.448813883139630 1977-01-01 1.439480722935050 1978-01-01 1.447794222903290 1979-01-01 1.452985168690390 1980-01-01 1.437953767517540 1981-01-01 1.400927825854220 1982-01-01 1.338663102278600 1983-01-01 1.275198314526040 1984-01-01 1.229978808899350 1985-01-01 1.208653594545710 1986-01-01 1.181414708962940 1987-01-01 1.172921693733270 1988-01-01 1.176979301856630 1989-01-01 1.184538191832430 1990-01-01 1.188867278007330 1991-01-01 1.166685109739670 1992-01-01 1.138337776682980 1993-01-01 1.107046509362800 1994-01-01 1.077431650295490 1995-01-01 1.050465121977120 1996-01-01 1.050555810534340 1997-01-01 1.065773830467290 1998-01-01 1.086413837207050 1999-01-01 1.098936403046420 2000-01-01 1.096983288033790 2001-01-01 1.050350688147320 2002-01-01 1.005037590897890 2003-01-01 0.966185382310528 2004-01-01 0.937589210776796 2005-01-01 0.919214544971768 2006-01-01 0.844214609906998 2007-01-01 0.795176492914456 2008-01-01 0.765896008254962 2009-01-01 0.752074671882853 2010-01-01 0.750469973221078 2011-01-01 0.810737419248830 2012-01-01 0.875528470292467 2013-01-01 0.937802948903447 2014-01-01 0.988196607887648 2015-01-01 1.021858356868720 2016-01-01 1.084176986048610 2017-01-01 1.143790867055770