# year    value 
 1980 10.00473 
 1981 10.73991 
 1982 11.28452 
 1983 11.28038 
 1984 10.39537 
 1985 10.31892 
 1986 10.66693 
 1987 10.53511 
 1988 11.33136 
 1989 11.47262 
 1990  11.6794 
 1991 10.74277 
 1992 11.66554 
 1993 11.13715 
 1994 12.31439 
 1995 11.29024 
 1996  10.4858 
 1997 11.50487 
 1998 11.51111 
 1999 11.61294 
 2000 12.29279 
 2001 11.54762 
 2002 12.12671 
 2003 11.82907 
 2004 11.35958 
 2005  11.0467 
 2006 11.79239 
 2007 12.20668 
 2008 11.95749 
 2009 11.99998 
 2010  10.9981 
 2011  12.2972 
 2012  12.0328 
 2013 11.65831 
 2014 12.76624 
 2015 12.59859 
 2016 12.15255 
 2017 12.17799 
 2018 12.93983