# year    value 
 1980 10.64908 
 1981 11.95697 
 1982 10.16313 
 1983 9.580716 
 1984 10.40376 
 1985 12.28026 
 1986 12.28944 
 1987 11.97267 
 1988 11.54624 
 1989 11.35818 
 1990 11.16938 
 1991 11.64565 
 1992 12.16788 
 1993 10.92605 
 1994 12.04546 
 1995   9.9705 
 1996 10.18004 
 1997 9.918966 
 1998 10.74909 
 1999  10.8082 
 2000 12.18837 
 2001 11.28851 
 2002 9.641039 
 2003 11.18682 
 2004  12.1729 
 2005 11.30718 
 2006 12.37672 
 2007 12.05178 
 2008 10.51468 
 2009 10.82422 
 2010 11.28182 
 2011 10.75488 
 2012 13.61452 
 2013  10.1378 
 2014 11.00263 
 2015  11.9588 
 2016 12.32005 
 2017 12.15993 
 2018 11.61255