Year	Percent of Total
1960-01-01	43.6526109636571
1961-01-01	43.9248570226667
1962-01-01	44.1708580317083
1963-01-01	44.3727341231250
1964-01-01	44.4979197350593
1965-01-01	44.5340718787844
1966-01-01	44.6849323672206
1967-01-01	44.7102942318737
1968-01-01	44.6461486592043
1969-01-01	44.5329151687790
1970-01-01	44.3881745908068
1971-01-01	44.3103076508273
1972-01-01	44.1761350312482
1973-01-01	43.9954517164316
1974-01-01	43.7762664616981
1975-01-01	43.5266583659155
1976-01-01	43.3527424502239
1977-01-01	43.1620545829257
1978-01-01	42.9385868714626
1979-01-01	42.6541823091894
1980-01-01	42.2968503011674
1981-01-01	42.0319764188931
1982-01-01	41.6430123786537
1983-01-01	41.1846902422821
1984-01-01	40.7321489305736
1985-01-01	40.3211652152095
1986-01-01	39.9184187157464
1987-01-01	39.5868365041358
1988-01-01	39.2814502416201
1989-01-01	38.9327385238491
1990-01-01	38.5116081444993
1991-01-01	38.1773734818559
1992-01-01	37.7528339640805
1993-01-01	37.2736586268907
1994-01-01	36.7936153720703
1995-01-01	36.3360090121121
1996-01-01	35.9399550117969
1997-01-01	35.5570735017585
1998-01-01	35.1771374856606
1999-01-01	34.7801925089957
2000-01-01	34.3549626452047
2001-01-01	33.8360008199117
2002-01-01	33.3164520588282
2003-01-01	32.7850541868066
2004-01-01	32.2396562720157
2005-01-01	31.6907644616650
2006-01-01	31.2191537843511
2007-01-01	30.7303390087148
2008-01-01	30.2409470295001
2009-01-01	29.7786904659816
2010-01-01	29.3617482827974
2011-01-01	29.0136599176834
2012-01-01	28.7127383611229
2013-01-01	28.4434495170995
2014-01-01	28.1766256247225
2015-01-01	27.8956234713364
2016-01-01	27.6557170192749
2017-01-01	27.3852391779574