Year	Index
1981-01-01	45.2
1988-01-01	43.8
1990-01-01	45.3
1992-01-01	47.9
1994-01-01	43.5
1996-01-01	42.9
1998-01-01	41.5
1999-01-01	43.1
2000-01-01	42.8
2002-01-01	41.9
2004-01-01	42.5
2006-01-01	41.8
2007-01-01	39.8
2008-01-01	40.3
2009-01-01	39.6
2010-01-01	39.4
2011-01-01	37.5
2012-01-01	39.3
2013-01-01	37.8
2014-01-01	37.0
2015-01-01	36.0