Year	Percent of Total
1960-01-01	7.57518364344796
1961-01-01	7.70338087791125
1962-01-01	7.85314495279268
1963-01-01	8.02392900402937
1964-01-01	8.21186355700771
1965-01-01	8.41674095496852
1966-01-01	8.64114017600689
1967-01-01	8.87090578442544
1968-01-01	9.10784973045574
1969-01-01	9.35589220463751
1970-01-01	9.61772915962384
1971-01-01	9.88068888679102
1972-01-01	10.13499157994250
1973-01-01	10.38124818471680
1974-01-01	10.62323524201650
1975-01-01	10.86410826927380
1976-01-01	11.13183361479890
1977-01-01	11.40401175430040
1978-01-01	11.64590359734360
1979-01-01	11.80225832798970
1980-01-01	11.84743390839390
1981-01-01	11.79433870753840
1982-01-01	11.63100734536070
1983-01-01	11.43365954531370
1984-01-01	11.31105237947850
1985-01-01	11.32596146464780
1986-01-01	11.58130498974140
1987-01-01	11.93715018583840
1988-01-01	12.35183751415670
1989-01-01	12.76483161572430
1990-01-01	13.14352717468820
1991-01-01	13.57698111873200
1992-01-01	13.98124741319490
1993-01-01	14.36526288994650
1994-01-01	14.73855793069910
1995-01-01	15.10473578560190
1996-01-01	15.48417534665270
1997-01-01	15.83760831766670
1998-01-01	16.15171321540450
1999-01-01	16.40736576940560
2000-01-01	16.59263993902310
2001-01-01	16.85290016601630
2002-01-01	17.04063494856270
2003-01-01	17.17253248736110
2004-01-01	17.27138581352770
2005-01-01	17.35403603677000
2006-01-01	17.48863174215100
2007-01-01	17.60724170336020
2008-01-01	17.73196148079230
2009-01-01	17.89633357161920
2010-01-01	18.12306960952600
2011-01-01	18.46871481290710
2012-01-01	18.87433257600870
2013-01-01	19.30753889857080
2014-01-01	19.71833852685040
2015-01-01	20.07647341737870
2016-01-01	20.47434941402180
2017-01-01	20.80092076146880