# year    value 
 1980 12.45827 
 1981  12.2812 
 1982 13.09371 
 1983 12.95938 
 1984 12.90163 
 1985 12.78317 
 1986 12.84333 
 1987 13.30577 
 1988 12.90947 
 1989 12.66428 
 1990 12.91146 
 1991 12.73161 
 1992 12.57209 
 1993 12.74604 
 1994 13.48785 
 1995 13.16436 
 1996 12.69591 
 1997 13.42292 
 1998 12.70387 
 1999 12.59767 
 2000 12.56771 
 2001 12.49066 
 2002 13.14581 
 2003  13.3174 
 2004 13.30488 
 2005 12.29527 
 2006 12.94837 
 2007 12.63058 
 2008 13.07115 
 2009 13.07187 
 2010  12.5512 
 2011 13.01699 
 2012 13.37789 
 2013 12.71513 
 2014 13.53956 
 2015 13.00417 
 2016 13.01091 
 2017 12.95614 
 2018 13.25264