# year    value 
 1979  11.2833 
 1980 11.30581 
 1981  11.2207 
 1982 11.41284 
 1983 11.52841 
 1984 10.74176 
 1985 11.02772 
 1986 11.14616 
 1987 11.36015 
 1988 11.31312 
 1989 11.16719 
 1990 11.31866 
 1991 11.42154 
 1992 11.08928 
 1993 11.27016 
 1994  11.7373 
 1995 11.76751 
 1996 11.27607 
 1997 11.81138 
 1998 12.03799 
 1999 11.17531 
 2000 11.17386 
 2001 11.44989 
 2002 11.53627 
 2003 11.88503 
 2004 11.63457 
 2005 11.58189 
 2006 11.95273 
 2007 11.42608 
 2008 11.45395 
 2009  11.8318 
 2010 11.84797 
 2011 11.52363 
 2012 11.88899 
 2013 11.67386 
 2014 11.85564 
 2015 12.14011 
 2016 12.17052 
 2017 11.96349 
 2018 11.76276