Year	Percent of Total
1960-01-01	67.3843648483790
1961-01-01	67.2562405568996
1962-01-01	67.1215868406196
1963-01-01	66.9886164216057
1964-01-01	66.8751798906265
1965-01-01	66.7889018726116
1966-01-01	66.6447010973329
1967-01-01	66.5567509181249
1968-01-01	66.5073564346011
1969-01-01	66.4575092421932
1970-01-01	66.3836297217387
1971-01-01	66.3177917057209
1972-01-01	66.2190320589083
1973-01-01	66.1315119911275
1974-01-01	66.1218883854379
1975-01-01	66.2112320384088
1976-01-01	66.0617819570773
1977-01-01	66.0859421944357
1978-01-01	66.2327428468903
1979-01-01	66.4199845923236
1980-01-01	66.6011339006141
1981-01-01	66.7976814026637
1982-01-01	66.9068610895269
1983-01-01	66.9557380513045
1984-01-01	66.9949810986827
1985-01-01	67.0345569952312
1986-01-01	66.9184455475489
1987-01-01	66.8466126790562
1988-01-01	66.7917568771627
1989-01-01	66.7271663906328
1990-01-01	66.6680553303668
1991-01-01	66.2885708332327
1992-01-01	65.9638064517606
1993-01-01	65.7177705070374
1994-01-01	65.5746018866011
1995-01-01	65.5396330755803
1996-01-01	65.7652315108973
1997-01-01	66.0494712840082
1998-01-01	66.3847273885261
1999-01-01	66.7589251232304
2000-01-01	67.1550141496198
2001-01-01	67.4446734334544
2002-01-01	67.6947659413194
2003-01-01	67.9387624551398
2004-01-01	68.1975377985875
2005-01-01	68.4626393716116
2006-01-01	68.3338703581619
2007-01-01	68.2496572691240
2008-01-01	68.1566807757884
2009-01-01	67.9907649667251
2010-01-01	67.7325603346724
2011-01-01	67.3592695411645
2012-01-01	66.9324623712842
2013-01-01	66.4732279359305
2014-01-01	66.0188232376465
2015-01-01	65.5854000400469
2016-01-01	65.2335666039086
2017-01-01	64.8399985638595