# year    value 
 1980 13.98417 
 1981 13.89864 
 1982 13.66589 
 1983 14.23987 
 1984  13.6186 
 1985 13.71829 
 1986 13.67078 
 1987 13.95323 
 1988 14.10845 
 1989 13.91624 
 1990 14.20298 
 1991 14.10291 
 1992 13.48385 
 1993 13.64457 
 1994 14.28322 
 1995 14.38017 
 1996 13.86192 
 1997 14.31232 
 1998 14.31646 
 1999 14.27794 
 2000 13.91762 
 2001 14.46926 
 2002 14.39806 
 2003 14.53301 
 2004 14.57262 
 2005 14.87767 
 2006 14.56325 
 2007 14.63273 
 2008  14.6464 
 2009 14.60053 
 2010 14.79669 
 2011 14.52351 
 2012 14.66738 
 2013 14.65451 
 2014 14.55691 
 2015 14.86737 
 2016 14.63947 
 2017 14.69598 
 2018 14.59833