# year    value 
 1980 9.466721 
 1981 10.10584 
 1982 8.427517 
 1983 9.017495 
 1984 8.675539 
 1985 8.444408 
 1986 9.762961 
 1987 9.597067 
 1988 9.672884 
 1989  9.46801 
 1990 9.375165 
 1991 9.197936 
 1992 9.820027 
 1993 8.725974 
 1994 9.978471 
 1995 9.783169 
 1996 9.713129 
 1997  9.33259 
 1998 9.274513 
 1999 9.645873 
 2000 9.829847 
 2001 9.873447 
 2002 9.657271 
 2003  10.4359 
 2004 9.809241 
 2005 9.965967 
 2006 10.09189 
 2007 10.21466 
 2008 9.533873 
 2009 9.582719 
 2010 9.653575 
 2011 9.349814 
 2012 10.81502 
 2013 9.615404 
 2014 10.58175 
 2015  10.9507 
 2016 10.70397 
 2017 10.68631 
 2018  10.6244