Year	Percent of Total
1960-01-01	45.4051070599503
1961-01-01	45.6678955212173
1962-01-01	45.8518842723253
1963-01-01	46.0242011448446
1964-01-01	46.1711052580236
1965-01-01	46.2790134746241
1966-01-01	46.9933184855234
1967-01-01	47.5459191418307
1968-01-01	47.9339556333773
1969-01-01	48.1376015058460
1970-01-01	48.1231257926490
1971-01-01	47.7992937159428
1972-01-01	47.3878652414097
1973-01-01	46.8742815100934
1974-01-01	46.2726432215868
1975-01-01	45.5935618236972
1976-01-01	44.6220897662850
1977-01-01	43.8008749100172
1978-01-01	43.0913707806138
1979-01-01	42.4138678223185
1980-01-01	41.7022374659972
1981-01-01	41.6979658223920
1982-01-01	41.5196251107482
1983-01-01	41.2395760018769
1984-01-01	40.9795187655847
1985-01-01	40.7948655178653
1986-01-01	40.4365606245685
1987-01-01	40.0385658586201
1988-01-01	39.6907053144179
1989-01-01	39.4758187698174
1990-01-01	39.3965508181560
1991-01-01	39.3368508281498
1992-01-01	39.5126497444919
1993-01-01	39.7432144201414
1994-01-01	39.7983992987802
1995-01-01	39.6217577750947
1996-01-01	39.5915699031846
1997-01-01	39.2587231842853
1998-01-01	38.8088742471817
1999-01-01	38.4984271090572
2000-01-01	38.4382455496421
2001-01-01	37.9906906937360
2002-01-01	37.8962332634296
2003-01-01	38.0152120975258
2004-01-01	38.1421428998267
2005-01-01	38.1557981413486
2006-01-01	38.1250676080992
2007-01-01	37.9895854704612
2008-01-01	37.7758361244600
2009-01-01	37.5535693602563
2010-01-01	37.3565591480454
2011-01-01	37.2902263403999
2012-01-01	37.1973587674248
2013-01-01	37.0746620082029
2014-01-01	36.9174339679719
2015-01-01	36.7210710390734
2016-01-01	36.2819962285992
2017-01-01	35.8313275319385