Year	Percent of Total
1960-01-01	22.2327821342129
1961-01-01	22.4609071229347
1962-01-01	22.6583741719277
1963-01-01	22.8656587835072
1964-01-01	23.1167442635436
1965-01-01	23.4106914593771
1966-01-01	23.6942754861104
1967-01-01	23.9991748196709
1968-01-01	24.2886324615949
1969-01-01	24.4972889340860
1970-01-01	24.5848089716147
1971-01-01	24.5348421395593
1972-01-01	24.3637975775865
1973-01-01	24.0821525778996
1974-01-01	23.7214949864220
1975-01-01	23.3031352808421
1976-01-01	22.7783428038272
1977-01-01	22.2432147601229
1978-01-01	21.6870512033744
1979-01-01	21.1076199112509
1980-01-01	20.5211549601091
1981-01-01	19.9761510040156
1982-01-01	19.4565875240276
1983-01-01	18.9718091379019
1984-01-01	18.5258146360341
1985-01-01	18.1192766571922
1986-01-01	17.8379527455175
1987-01-01	17.5219966300807
1988-01-01	17.2240704858699
1989-01-01	17.0145026937886
1990-01-01	16.9303163446574
1991-01-01	16.9524467749370
1992-01-01	17.1250986312870
1993-01-01	17.3840731081744
1994-01-01	17.6077412837639
1995-01-01	17.7173787480815
1996-01-01	17.6944031096565
1997-01-01	17.5340687444945
1998-01-01	17.2787509093962
1999-01-01	17.0241803835072
2000-01-01	16.8271478135089
2001-01-01	16.6030605052170
2002-01-01	16.4492037039678
2003-01-01	16.3321571867984
2004-01-01	16.1838208403388
2005-01-01	15.9717579495132
2006-01-01	15.7616025135385
2007-01-01	15.4953756612751
2008-01-01	15.2015367838615
2009-01-01	14.9323455879173
2010-01-01	14.7166647502856
2011-01-01	14.5236731938008
2012-01-01	14.3736319419626
2013-01-01	14.2678375365567
2014-01-01	14.1881592268007
2015-01-01	14.1199611875432
2016-01-01	14.0962544551354
2017-01-01	14.0916103606762