# year    value 
 1980 13.27579 
 1981 13.53112 
 1982 13.08872 
 1983 13.46417 
 1984  13.0631 
 1985 13.08781 
 1986 13.26424 
 1987   13.412 
 1988  13.5594 
 1989 13.36128 
 1990 13.64446 
 1991 13.51321 
 1992 13.21404 
 1993 13.33693 
 1994 13.49213 
 1995 13.76269 
 1996 13.33751 
 1997  13.6118 
 1998 13.95871 
 1999 13.73528 
 2000 13.59777 
 2001 13.80345 
 2002 13.90487 
 2003 13.89999 
 2004  13.7901 
 2005 14.04376 
 2006 13.95272 
 2007 14.04784 
 2008  13.8226 
 2009 13.84988 
 2010 14.07428 
 2011 13.85595 
 2012 13.89461 
 2013  13.9379 
 2014 13.98022 
 2015 14.25259 
 2016 14.38873 
 2017 14.24464 
 2018 14.03128