Annual Percent of Total
1960-01-01 31.1776819769864
1961-01-01 31.5016651228660
1962-01-01 31.7718896992189
1963-01-01 32.0153409586162
1964-01-01 32.2624186456760
1965-01-01 32.5324735075895
1966-01-01 32.9392119169046
1967-01-01 33.3198512882275
1968-01-01 33.6847667232754
1969-01-01 34.0355089360465
1970-01-01 34.3688889340776
1971-01-01 35.0374170518056
1972-01-01 35.6187910093081
1973-01-01 36.1401553902286
1974-01-01 36.6316106901881
1975-01-01 37.1043655997390
1976-01-01 37.6283953779171
1977-01-01 38.1148953849146
1978-01-01 38.5577460085328
1979-01-01 38.9452070388865
1980-01-01 39.2746986596888
1981-01-01 39.6681590236320
1982-01-01 39.9893069745910
1983-01-01 40.2528293687652
1984-01-01 40.4798764483351
1985-01-01 40.6817374124337
1986-01-01 40.9559134704998
1987-01-01 41.1745050253004
1988-01-01 41.3485708707450
1989-01-01 41.4826110323303
1990-01-01 41.5762456259740
1991-01-01 41.7081790143965
1992-01-01 41.7851128124888
1993-01-01 41.8091447052072
1994-01-01 41.7804343780788
1995-01-01 41.6990674288787
1996-01-01 41.5978003472191
1997-01-01 41.4515496479107
1998-01-01 41.2628156526847
1999-01-01 41.0329013060753
2000-01-01 40.7654156127500
2001-01-01 40.4565148673925
2002-01-01 40.1010808793820
2003-01-01 39.7225154463440
2004-01-01 39.3501709787019
2005-01-01 39.0026982608832
2006-01-01 38.5182068098701
2007-01-01 38.0761257943060
2008-01-01 37.6787200820614
2009-01-01 37.3193954450406
2010-01-01 36.9964821577725
2011-01-01 36.7351147633523
2012-01-01 36.4775614079327
2013-01-01 36.2338913678807
2014-01-01 35.9993773034574
2015-01-01 35.7614205965780
2016-01-01 35.8623103709189
2017-01-01 35.9021142767131