Year	Percent of Total
1960-01-01	39.5316676404658
1961-01-01	40.7251037138490
1962-01-01	41.8978646385827
1963-01-01	42.9396764128434
1964-01-01	43.7228848591409
1965-01-01	44.1900357313162
1966-01-01	44.6586007698784
1967-01-01	44.7390000144513
1968-01-01	44.5401477954169
1969-01-01	44.2105667862135
1970-01-01	43.8158696145289
1971-01-01	43.2294666774655
1972-01-01	42.6404113296518
1973-01-01	41.9833801561311
1974-01-01	41.1706631760056
1975-01-01	40.1869923126636
1976-01-01	39.2045797302835
1977-01-01	38.1002549148629
1978-01-01	36.9444650985267
1979-01-01	35.8519701766457
1980-01-01	34.8936664185664
1981-01-01	34.1203202908476
1982-01-01	33.5008515553366
1983-01-01	33.0305470673315
1984-01-01	32.6902358108968
1985-01-01	32.4676308472794
1986-01-01	32.5345980524392
1987-01-01	32.6860520780445
1988-01-01	32.8724132087196
1989-01-01	33.0513263076424
1990-01-01	33.2025040143481
1991-01-01	33.4631655856599
1992-01-01	33.6268004544473
1993-01-01	33.7071295177994
1994-01-01	33.7083562118243
1995-01-01	33.6129493097870
1996-01-01	33.3419047646932
1997-01-01	32.9654316878487
1998-01-01	32.4715290696859
1999-01-01	31.8600344543945
2000-01-01	31.1477246412264
2001-01-01	30.1765134503779
2002-01-01	29.2072443990980
2003-01-01	28.2271817296686
2004-01-01	27.2289398763055
2005-01-01	26.2294805498696
2006-01-01	25.4273049450215
2007-01-01	24.6182618120597
2008-01-01	23.8639419046311
2009-01-01	23.2539932345085
2010-01-01	22.8353481228862
2011-01-01	22.6109917378232
2012-01-01	22.5695491929393
2013-01-01	22.6680829250616
2014-01-01	22.8049792024661
2015-01-01	22.9104826168674
2016-01-01	23.1686980534223
2017-01-01	23.2774386474648