Year	Percent
1978-01-01	82.2774133165927
1979-01-01	82.1513217948926
1980-01-01	81.8609977336876
1981-01-01	81.8752151258270
1982-01-01	81.6709379997037
1983-01-01	81.7225580382502
1984-01-01	81.1586978013981
1985-01-01	80.5525685972572
1986-01-01	80.2109621200220
1987-01-01	79.9284282229900
1988-01-01	79.7433329027988
1989-01-01	79.6967785587906
1990-01-01	79.9631201368122
1991-01-01	80.4645414917667
1992-01-01	80.9141576135748
1993-01-01	81.0490936232129
1994-01-01	80.8910395709182
1995-01-01	80.7829074585337
1996-01-01	80.9842272213170
1997-01-01	81.0743543940465
1998-01-01	80.7231281878623
1999-01-01	80.4789529508854
2000-01-01	80.1760051904541
2001-01-01	79.7056105043225
2002-01-01	79.0751956809161
2003-01-01	78.7015139906164
2004-01-01	78.2583780608428
2005-01-01	78.3324184877654
2006-01-01	78.5498306124384
2007-01-01	78.8262231446050
2008-01-01	78.7742366610566
2009-01-01	78.2632882637644
2010-01-01	78.1390640355907
2011-01-01	77.9287808596684
2012-01-01	77.6765506148579
2013-01-01	77.7862242423966
2014-01-01	77.8559096320972
2015-01-01	78.0327331548305
2016-01-01	78.4957706913652
2017-01-01	78.7456163708756