Year	Percent of Total
1960-01-01	7.77846476541263
1961-01-01	7.99638973341401
1962-01-01	8.22703648689467
1963-01-01	8.46810543357243
1964-01-01	8.71446020325807
1965-01-01	8.96120984341802
1966-01-01	9.16496198373769
1967-01-01	9.35906795643974
1968-01-01	9.53900868151662
1969-01-01	9.70375173088673
1970-01-01	9.85780264629269
1971-01-01	10.13514116283370
1972-01-01	10.38805882092660
1973-01-01	10.61499657597730
1974-01-01	10.81297176534390
1975-01-01	10.97908153398640
1976-01-01	11.14005492884990
1977-01-01	11.28559363850830
1978-01-01	11.39499501015790
1979-01-01	11.43137489318780
1980-01-01	11.37911481248060
1981-01-01	11.17359060507450
1982-01-01	10.85513722520930
1983-01-01	10.46824141025080
1984-01-01	10.10889652285290
1985-01-01	9.85186118187170
1986-01-01	9.88202521095311
1987-01-01	10.01438446033510
1988-01-01	10.21563420821640
1989-01-01	10.43389560456860
1990-01-01	10.63988210193080
1991-01-01	10.97254622278980
1992-01-01	11.29905979121540
1993-01-01	11.62188719531700
1994-01-01	11.95039905151670
1995-01-01	12.29050672065690
1996-01-01	12.68669660817630
1997-01-01	13.07534627292870
1998-01-01	13.44744604562630
1999-01-01	13.79185824400320
2000-01-01	14.10435710553540
2001-01-01	14.42191486504630
2002-01-01	14.71399170331510
2003-01-01	14.98658850206010
2004-01-01	15.24477385597280
2005-01-01	15.49225785347850
2006-01-01	15.76047601770840
2007-01-01	16.01175840150100
2008-01-01	16.24568173084430
2009-01-01	16.46413720188030
2010-01-01	16.67369135445110
2011-01-01	16.89193137745710
2012-01-01	17.10452875426500
2013-01-01	17.34353151972370
2014-01-01	17.64685430343650
2015-01-01	18.03471005230410
2016-01-01	18.51167209371940
2017-01-01	19.06175840490470