Year	Percent
1960-01-01	15.0069678006463
1961-01-01	15.0178416926792
1962-01-01	15.6784046106502
1963-01-01	16.8566627512974
1964-01-01	17.8213317198379
1965-01-01	18.2612599458568
1966-01-01	18.2745524255621
1967-01-01	18.2997324597156
1968-01-01	17.7846918532294
1969-01-01	18.0141734548147
1970-01-01	18.0899508141870
1971-01-01	17.6811972661386
1972-01-01	17.7589513941304
1973-01-01	17.7060397799072
1974-01-01	17.9753811577189
1975-01-01	18.4272957046869
1976-01-01	18.6532192356285
1977-01-01	19.2204060436575
1978-01-01	19.3930943233676
1979-01-01	19.5692795111880
1980-01-01	19.8603070916651
1981-01-01	19.8742109247618
1982-01-01	20.1589280643508
1983-01-01	20.1779101308116
1984-01-01	20.7449779174422
1985-01-01	21.3881288504693
1986-01-01	21.7418587214327
1987-01-01	22.1987376287116
1988-01-01	22.4827786159895
1989-01-01	22.5942324891034
1990-01-01	22.4134669957837
1991-01-01	22.0254263265879
1992-01-01	21.8433795590664
1993-01-01	21.8634481909517
1994-01-01	22.1210817841458
1995-01-01	22.3092461159387
1996-01-01	22.2062631301974
1997-01-01	22.1612893807262
1998-01-01	22.6261469901714
1999-01-01	22.9600265573703
2000-01-01	23.4935463598880
2001-01-01	24.2375555113978
2002-01-01	25.2098984550227
2003-01-01	25.8099459238234
2004-01-01	26.4734169054664
2005-01-01	26.6337239427068
2006-01-01	26.7434609446958
2007-01-01	26.7772452745079
2008-01-01	27.1361401048258
2009-01-01	27.8628719349969
2010-01-01	28.2109182513434
2011-01-01	28.6863284713433
2012-01-01	29.2022758337320
2013-01-01	29.4109649468353
2014-01-01	29.5341092603344
2015-01-01	29.6255929421654
2016-01-01	29.4935918755616
2017-01-01	29.4373202056755