# year    value 
 1979   8.0948 
 1980 9.025742 
 1981 9.181188 
 1982 8.758364 
 1983 9.251537 
 1984 8.657216 
 1985 8.230607 
 1986 8.837379 
 1987  8.87729 
 1988  9.17695 
 1989 8.959888 
 1990 9.070457 
 1991  9.13145 
 1992 9.053279 
 1993 9.001984 
 1994 8.567964 
 1995  9.52989 
 1996 8.965546 
 1997  9.00796 
 1998 9.463627 
 1999 9.567198 
 2000 9.358769 
 2001 8.916971 
 2002  9.68463 
 2003 9.263629 
 2004 9.632421 
 2005 9.388664 
 2006 9.502031 
 2007 10.08706 
 2008 9.207316 
 2009 9.476182 
 2010 9.544239 
 2011 9.177358 
 2012 9.314798 
 2013 9.442359 
 2014 9.306921 
 2015 9.743899 
 2016 10.57231 
 2017 10.00521 
 2018 9.852814