Year	Percent of Total
1960-01-01	6.08522816164099
1961-01-01	6.18237161180596
1962-01-01	6.28267800472066
1963-01-01	6.39413639021734
1964-01-01	6.52219662892791
1965-01-01	6.67200700484548
1966-01-01	6.85725220806390
1967-01-01	7.05677498068034
1968-01-01	7.26910682843892
1969-01-01	7.49084315640420
1970-01-01	7.72033746942931
1971-01-01	7.98976334281998
1972-01-01	8.23778901454512
1973-01-01	8.48045659919738
1974-01-01	8.74180942997764
1975-01-01	9.03141729904740
1976-01-01	9.32666630460221
1977-01-01	9.65366950087192
1978-01-01	9.96396128074105
1979-01-01	10.18633641008410
1980-01-01	10.28729806326600
1981-01-01	10.31051324800250
1982-01-01	10.22614314905410
1983-01-01	10.08258353479760
1984-01-01	9.94641876507641
1985-01-01	9.85643972636497
1986-01-01	9.85208661754703
1987-01-01	9.86562973773007
1988-01-01	9.92462124537899
1989-01-01	10.06550088071020
1990-01-01	10.30546217125790
1991-01-01	10.63882288875630
1992-01-01	11.06839172110070
1993-01-01	11.52215643791150
1994-01-01	11.89552141909420
1995-01-01	12.13465094294790
1996-01-01	12.32569010597710
1997-01-01	12.35438536437540
1998-01-01	12.30972437213940
1999-01-01	12.31889286597350
2000-01-01	12.44265829991010
2001-01-01	12.74433723025660
2002-01-01	13.14582011230950
2003-01-01	13.54842225866300
2004-01-01	13.79976551291500
2005-01-01	13.81910166877540
2006-01-01	13.81364488263720
2007-01-01	13.64564695995900
2008-01-01	13.40489711065770
2009-01-01	13.20301344376150
2010-01-01	13.08672418766410
2011-01-01	13.11996563993460
2012-01-01	13.16630413970460
2013-01-01	13.22779137174160
2014-01-01	13.32599010006710
2015-01-01	13.48862411073550
2016-01-01	13.79060824524170
2017-01-01	14.17844772482910