Year	Percent of Total
1960-01-01	46.5547664558191
1961-01-01	47.0103890550067
1962-01-01	47.3641934073909
1963-01-01	47.6079187246517
1964-01-01	47.7322860569574
1965-01-01	47.7291414826314
1966-01-01	47.6710292075043
1967-01-01	47.5800855488695
1968-01-01	47.4471905396228
1969-01-01	47.2740731158686
1970-01-01	47.0780243256815
1971-01-01	46.4310535194848
1972-01-01	45.8186739211134
1973-01-01	45.2731547191732
1974-01-01	44.8209452637200
1975-01-01	44.4602804082908
1976-01-01	44.0536479861451
1977-01-01	43.7187181935511
1978-01-01	43.3637396526538
1979-01-01	42.9233214901308
1980-01-01	42.3854038887244
1981-01-01	41.7072602886923
1982-01-01	41.0888503749139
1983-01-01	40.5292779492341
1984-01-01	39.9710275418946
1985-01-01	39.3503670004608
1986-01-01	38.7198005386816
1987-01-01	37.9775209701309
1988-01-01	37.2072020470715
1989-01-01	36.5654818182428
1990-01-01	36.1501071559742
1991-01-01	35.8955996931300
1992-01-01	35.8433114923262
1993-01-01	35.9395819951054
1994-01-01	36.0474561609406
1995-01-01	36.0823916216007
1996-01-01	35.9698160163074
1997-01-01	35.8222771561189
1998-01-01	35.7513404542768
1999-01-01	35.8686470412219
2000-01-01	36.1650920415611
2001-01-01	36.1716580504425
2002-01-01	36.2816604689021
2003-01-01	36.3942877435470
2004-01-01	36.3829272056750
2005-01-01	36.1966106750685
2006-01-01	35.5226313732239
2007-01-01	34.7753416708006
2008-01-01	33.9906527279403
2009-01-01	33.2699918062795
2010-01-01	32.6751107753471
2011-01-01	31.9793085035376
2012-01-01	31.3733665652624
2013-01-01	30.8353592821875
2014-01-01	30.3246165474402
2015-01-01	29.8248307773183
2016-01-01	29.4183521853659
2017-01-01	28.9976718145577