Year	Index
1987-01-01	33.3
1990-01-01	33.2
1996-01-01	28.7
1998-01-01	33.1
2001-01-01	30.4
2004-01-01	32.5
2005-01-01	32.7
2007-01-01	31.6
2010-01-01	29.8
2011-01-01	30.9
2013-01-01	30.7
2015-01-01	33.5