# year    value 
 1980 10.69797 
 1981 10.29169 
 1982 10.49095 
 1983  10.7293 
 1984  10.6103 
 1985 10.99005 
 1986 10.43984 
 1987 10.86729 
 1988 10.76293 
 1989 10.83296 
 1990 10.62748 
 1991 10.46306 
 1992   10.198 
 1993 10.60069 
 1994 10.55125 
 1995  10.6671 
 1996 10.76856 
 1997 10.60323 
 1998 10.81147 
 1999 11.17059 
 2000 10.13634 
 2001  10.6703 
 2002 10.60886 
 2003 10.82874 
 2004 10.90922 
 2005 10.84935 
 2006 11.00153 
 2007 10.79622 
 2008 11.10739 
 2009  10.3767 
 2010 10.83982 
 2011 11.02291 
 2012 11.05205 
 2013 10.87315 
 2014   11.233 
 2015  10.5706 
 2016 11.27232 
 2017 11.07051 
 2018 10.95103