Year	Percent of Total
1960-01-01	40.4046647905310
1961-01-01	40.6882140856181
1962-01-01	40.9839673448678
1963-01-01	41.2552571165607
1964-01-01	41.4426754558359
1965-01-01	41.5229169597787
1966-01-01	41.6715059253711
1967-01-01	41.6961771880286
1968-01-01	41.6301924402034
1969-01-01	41.5203953497169
1970-01-01	41.3907674073081
1971-01-01	41.3474493196175
1972-01-01	41.2642298879616
1973-01-01	41.1480386945675
1974-01-01	41.0002167894038
1975-01-01	40.8246833013532
1976-01-01	40.7612484461685
1977-01-01	40.6441771622484
1978-01-01	40.4916436525190
1979-01-01	40.3232578023342
1980-01-01	40.1502570336615
1981-01-01	40.0888306108738
1982-01-01	40.0090646817888
1983-01-01	39.9105956862846
1984-01-01	39.7859752711657
1985-01-01	39.6317464197988
1986-01-01	39.5865387204157
1987-01-01	39.4771584569959
1988-01-01	39.3204511207749
1989-01-01	39.1339045463822
1990-01-01	38.9241659209356
1991-01-01	38.7478594996825
1992-01-01	38.5367876703929
1993-01-01	38.2894451911305
1994-01-01	38.0004689483273
1995-01-01	37.6689080444010
1996-01-01	37.3543262924463
1997-01-01	37.0072239533759
1998-01-01	36.6288040349937
1999-01-01	36.2226260439698
2000-01-01	35.7945227106307
2001-01-01	35.4266181427653
2002-01-01	35.0252221455086
2003-01-01	34.6038121226044
2004-01-01	34.1789306941269
2005-01-01	33.7584423537667
2006-01-01	33.3907324275194
2007-01-01	33.0295585997724
2008-01-01	32.6680608367579
2009-01-01	32.2912152423720
2010-01-01	31.8905530135445
2011-01-01	31.4983566070397
2012-01-01	31.0684774024281
2013-01-01	30.6168000677310
2014-01-01	30.1690645945976
2015-01-01	29.7392346642917
2016-01-01	29.3086307543117
2017-01-01	28.9187514931363