# year    value 
 1980 9.474566 
 1981 9.373815 
 1982 9.202532 
 1983   8.9995 
 1984 8.592403 
 1985 9.850108 
 1986  9.51881 
 1987 9.764146 
 1988 9.405483 
 1989 9.270981 
 1990   9.5434 
 1991 9.594268 
 1992  9.18301 
 1993 9.611128 
 1994  9.77787 
 1995 9.125977 
 1996 9.459954 
 1997  9.66277 
 1998 10.00599 
 1999 9.690737 
 2000 9.294734 
 2001 9.797457 
 2002 9.480092 
 2003 9.659405 
 2004 9.852421 
 2005 9.895779 
 2006 9.827594 
 2007 8.832388 
 2008 9.602075 
 2009 9.984652 
 2010 9.220278 
 2011  9.59652 
 2012 9.467161 
 2013  9.99941 
 2014 10.15571 
 2015 10.07944 
 2016 9.735558 
 2017 10.25053 
 2018 9.413952