Year	Percent of Total
1960-01-01	6.82841498513560
1961-01-01	7.03087219189655
1962-01-01	7.25592690865966
1963-01-01	7.49177673085820
1964-01-01	7.71343045175660
1965-01-01	7.90548581887894
1966-01-01	8.07367275605193
1967-01-01	8.17572524991059
1968-01-01	8.24591899818512
1969-01-01	8.33364770102008
1970-01-01	8.46378671842999
1971-01-01	8.60093184347693
1972-01-01	8.78833530112551
1973-01-01	9.00549161403984
1974-01-01	9.22001526726453
1975-01-01	9.41589871115295
1976-01-01	9.68276306299990
1977-01-01	9.92162843180699
1978-01-01	10.10500597325660
1979-01-01	10.20024317644270
1980-01-01	10.19200404953640
1981-01-01	10.09673032988790
1982-01-01	9.91076343087262
1983-01-01	9.69716199080419
1984-01-01	9.53636051996508
1985-01-01	9.47581173984401
1986-01-01	9.57262927076184
1987-01-01	9.73135334050758
1988-01-01	9.93473203789645
1989-01-01	10.16287045723690
1990-01-01	10.40501166208230
1991-01-01	10.71413481236830
1992-01-01	11.05478297127870
1993-01-01	11.41013317211330
1994-01-01	11.74784755695960
1995-01-01	12.04965654204760
1996-01-01	12.44334532748730
1997-01-01	12.76424199298320
1998-01-01	13.03936218581850
1999-01-01	13.31524771315870
2000-01-01	13.61279182766840
2001-01-01	13.97677916370150
2002-01-01	14.36917664668190
2003-01-01	14.74805994720680
2004-01-01	15.04238956269330
2005-01-01	15.21714927401020
2006-01-01	15.41700727389230
2007-01-01	15.50719617328510
2008-01-01	15.53558882909270
2009-01-01	15.57991566088880
2010-01-01	15.68784032873810
2011-01-01	15.85817391808700
2012-01-01	16.07961428280000
2013-01-01	16.35069331825010
2014-01-01	16.66014611117880
2015-01-01	16.99972042531780
2016-01-01	17.41715817453090
2017-01-01	17.85032459986140