Year	Percent of Total
1960-01-01	40.4034595988326
1961-01-01	40.7090717548076
1962-01-01	41.0562706331435
1963-01-01	41.3795154293700
1964-01-01	41.5702191617876
1965-01-01	41.5876400211872
1966-01-01	41.7616284561478
1967-01-01	41.7471317161287
1968-01-01	41.6000864982863
1969-01-01	41.3978328065566
1970-01-01	41.1716515355102
1971-01-01	41.2191358024691
1972-01-01	41.2431937806808
1973-01-01	41.2427272475002
1974-01-01	41.2090083062079
1975-01-01	41.1432979708623
1976-01-01	41.3336358102894
1977-01-01	41.4568519517179
1978-01-01	41.5452460839233
1979-01-01	41.6433591693930
1980-01-01	41.7901585628411
1981-01-01	42.0932444751213
1982-01-01	42.3344110194740
1983-01-01	42.5468184569741
1984-01-01	42.7425339015007
1985-01-01	42.9224977270345
1986-01-01	43.2125376950578
1987-01-01	43.4064364785692
1988-01-01	43.5352902185861
1989-01-01	43.6506654707302
1990-01-01	43.8039037300198
1991-01-01	44.0240376673372
1992-01-01	44.1789846124437
1993-01-01	44.2841196353157
1994-01-01	44.3048657587572
1995-01-01	44.1864255810411
1996-01-01	44.3376814559563
1997-01-01	44.4204764986469
1998-01-01	44.4211698121329
1999-01-01	44.3534718802871
2000-01-01	44.2396168448232
2001-01-01	44.2822366256949
2002-01-01	44.2684828032651
2003-01-01	44.2115703715034
2004-01-01	44.1235295797393
2005-01-01	44.0154363570528
2006-01-01	43.9736847751155
2007-01-01	43.8874498637034
2008-01-01	43.7714699652489
2009-01-01	43.6345334884854
2010-01-01	43.4801100964687
2011-01-01	43.3731605403451
2012-01-01	43.2252040935449
2013-01-01	43.0468729345653
2014-01-01	42.8514179270034
2015-01-01	42.6501833969274
2016-01-01	42.4660880463610
2017-01-01	42.2587451805338