# year    value 
 1979 7.871917 
 1980 7.725324 
 1981 8.133553 
 1982  9.22008 
 1983 8.232616 
 1984 8.377986 
 1985 7.991663 
 1986 8.663108 
 1987 9.704531 
 1988 7.930676 
 1989 7.760931 
 1990 8.319095 
 1991 8.154078 
 1992 8.372065 
 1993 7.282978 
 1994 9.403398 
 1995 8.159388 
 1996 7.574519 
 1997  8.72575 
 1998 7.360422 
 1999 8.596705 
 2000  9.39992 
 2001 8.299804 
 2002 8.995458 
 2003  8.22736 
 2004 9.338165 
 2005 9.000525 
 2006 10.70535 
 2007  7.56274 
 2008  8.66462 
 2009  9.56661 
 2010 8.196096 
 2011 9.727546 
 2012 9.701556 
 2013 9.421562 
 2014 10.60168 
 2015 9.260918 
 2016 9.233274 
 2017 8.479641 
 2018 10.48307