# year    value 
 1979 10.66923 
 1980 10.13035 
 1981 10.19545 
 1982 8.499806 
 1983 10.06899 
 1984 8.479342 
 1985 7.344331 
 1986 8.740792 
 1987 10.89268 
 1988 10.86683 
 1989 10.19874 
 1990  10.5441 
 1991 10.11803 
 1992  9.83896 
 1993 9.271916 
 1994 9.213796 
 1995 11.24343 
 1996 9.384604 
 1997 10.12398 
 1998 10.42254 
 1999 11.27145 
 2000 8.487947 
 2001 11.48937 
 2002 9.819722 
 2003 10.75231 
 2004 9.571037 
 2005 10.51385 
 2006  9.82143 
 2007 10.54447 
 2008 11.08497 
 2009 10.30657 
 2010 10.53381 
 2011 10.69828 
 2012 11.63253 
 2013 9.700553 
 2014 11.15368 
 2015 11.01035 
 2016 11.47272 
 2017 11.06176 
 2018 10.31723