# year    value 
 1980 9.485435 
 1981  11.7365 
 1982 10.39255 
 1983 11.30454 
 1984 9.481745 
 1985  10.6804 
 1986 11.07507 
 1987 9.276718 
 1988 11.09184 
 1989 12.10424 
 1990 12.06105 
 1991 10.27153 
 1992 11.54011 
 1993 11.47947 
 1994 11.93407 
 1995 10.72024 
 1996 10.44767 
 1997  11.2505 
 1998 11.43354 
 1999 12.09977 
 2000 12.58116 
 2001 12.32178 
 2002 12.05472 
 2003 12.20208 
 2004  10.7211 
 2005 11.26217 
 2006 11.07511 
 2007 13.32754 
 2008 11.78235 
 2009 12.70764 
 2010 11.17221 
 2011 12.74213 
 2012 12.42206 
 2013 10.63604 
 2014 12.52571 
 2015 11.98101 
 2016 11.59753 
 2017 12.66766 
 2018  12.9075