# year    value 
 1980 10.60038 
 1981 10.90798 
 1982 10.83486 
 1983 10.79799 
 1984 9.963664 
 1985 10.37662 
 1986 10.50653 
 1987 10.69173 
 1988 10.51459 
 1989 10.82847 
 1990 10.29438 
 1991 10.90597 
 1992 10.09733 
 1993 10.30805 
 1994 10.72021 
 1995 10.66191 
 1996 10.52069 
 1997 10.90426 
 1998 11.09255 
 1999 10.79608 
 2000 10.40317 
 2001 10.25816 
 2002 10.32956 
 2003 11.11423 
 2004 10.70802 
 2005 10.29725 
 2006 10.43359 
 2007  10.6676 
 2008 10.53997 
 2009 11.40565 
 2010 11.18898 
 2011 10.60536 
 2012 10.80227 
 2013 11.10732 
 2014 10.69368 
 2015 11.50569 
 2016 11.17141 
 2017 11.10503 
 2018 11.13323