Year	Percent of Total
1960-01-01	45.6793606734890
1961-01-01	46.2288436088294
1962-01-01	46.9246968266647
1963-01-01	47.6417388781876
1964-01-01	48.2018736258155
1965-01-01	48.5341348649509
1966-01-01	48.6777858587436
1967-01-01	48.6384039270067
1968-01-01	48.4722973211017
1969-01-01	48.2765275221186
1970-01-01	48.1018463276869
1971-01-01	47.9300455444249
1972-01-01	47.7441154495951
1973-01-01	47.5638636742172
1974-01-01	47.4038902392303
1975-01-01	47.2739271529594
1976-01-01	47.1233483514114
1977-01-01	46.9935846695802
1978-01-01	46.8793695456481
1979-01-01	46.7665319042572
1980-01-01	46.6441860325743
1981-01-01	46.7034284575167
1982-01-01	46.7230355547831
1983-01-01	46.6954457814230
1984-01-01	46.5998200282813
1985-01-01	46.4175007610708
1986-01-01	46.2228869996169
1987-01-01	45.8894704954623
1988-01-01	45.4535119348480
1989-01-01	44.9624670803151
1990-01-01	44.4392675294213
1991-01-01	43.8072576939447
1992-01-01	43.2022079455542
1993-01-01	42.5811855678725
1994-01-01	41.8852789533231
1995-01-01	41.0979839321290
1996-01-01	40.5128860516439
1997-01-01	39.8194347336250
1998-01-01	39.0648798382870
1999-01-01	38.3173457610088
2000-01-01	37.6105974518903
2001-01-01	37.0796069370091
2002-01-01	36.5642800680692
2003-01-01	36.0683884791051
2004-01-01	35.5870181979195
2005-01-01	35.1220894769626
2006-01-01	34.6134617813673
2007-01-01	34.1509725691517
2008-01-01	33.7298873635845
2009-01-01	33.3455731200142
2010-01-01	32.9993160835510
2011-01-01	32.6995684282315
2012-01-01	32.4380000143588
2013-01-01	32.2094313056053
2014-01-01	31.9987844541088
2015-01-01	31.7915966751720
2016-01-01	31.6229235732760
2017-01-01	31.4059540219954