Year	Percent
1968-01-01	15.1122586207358
1969-01-01	15.2552383297440
1970-01-01	15.1197209224778
1971-01-01	14.5156964448374
1972-01-01	14.3713431950343
1973-01-01	14.2180834785895
1974-01-01	14.3373840157459
1975-01-01	14.6143384809532
1976-01-01	14.6542493427128
1977-01-01	15.1097721062174
1978-01-01	15.0803208987955
1979-01-01	15.0975288740925
1980-01-01	15.3344995100229
1981-01-01	15.2545952681596
1982-01-01	15.2503731909944
1983-01-01	15.2265707458061
1984-01-01	15.6489028453039
1985-01-01	16.2324688149905
1986-01-01	16.4694480708394
1987-01-01	16.7866330022234
1988-01-01	17.0597616854301
1989-01-01	17.0407962394157
1990-01-01	16.7433183518448
1991-01-01	16.2749358422226
1992-01-01	15.8148840412150
1993-01-01	15.5287226954403
1994-01-01	15.5227804836771
1995-01-01	15.4106629967094
1996-01-01	14.8829746207279
1997-01-01	14.5133412657906
1998-01-01	14.5807695572237
1999-01-01	14.5756310081307
2000-01-01	14.6233031080663
2001-01-01	14.8572757755301
2002-01-01	15.1530498018609
2003-01-01	15.2510818945772
2004-01-01	15.5839649034446
2005-01-01	15.4858841886878
2006-01-01	15.1358918792327
2007-01-01	14.6880453253131
2008-01-01	14.7100082954916
2009-01-01	15.0654362496582
2010-01-01	15.0644287136098
2011-01-01	15.1002845663828
2012-01-01	15.6166255454251
2013-01-01	15.3696877869987
2014-01-01	15.0709256279244
2015-01-01	14.9281542732790
2016-01-01	14.4478465556755
2017-01-01	14.3700477681609