# year    value 
 1980 10.86704 
 1981 11.49534 
 1982  12.7279 
 1983 11.25758 
 1984  11.7775 
 1985 11.17221 
 1986 11.85317 
 1987 12.81745 
 1988  10.9615 
 1989 11.22256 
 1990 11.67921 
 1991 11.69003 
 1992 11.66129 
 1993 10.49323 
 1994   12.407 
 1995 11.39552 
 1996  11.0128 
 1997 11.85337 
 1998 10.78817 
 1999 12.06584 
 2000 12.90624 
 2001 11.46558 
 2002 12.08388 
 2003 11.56271 
 2004 12.40518 
 2005 12.12593 
 2006  13.9481 
 2007 10.65642 
 2008 11.80182 
 2009 12.83851 
 2010 11.34803 
 2011 12.81173 
 2012 12.88909 
 2013 12.50316 
 2014  13.6835 
 2015 12.33953 
 2016 12.35764 
 2017 11.67834 
 2018 13.64148