Year	Index
1981-01-01	32.4
1987-01-01	31.5
1991-01-01	31
1994-01-01	31.3
1997-01-01	31.6
1998-01-01	33.2
2000-01-01	33.3
2004-01-01	33.7
2007-01-01	33.8
2010-01-01	33.6
2013-01-01	34