# year    value 
 1979 17.01136 
 1980 16.93509 
 1981 16.76558 
 1982 16.80255 
 1983 16.88369 
 1984 16.14136 
 1985 16.62149 
 1986 16.68211 
 1987  17.1273 
 1988 17.05944 
 1989 16.88862 
 1990 17.09291 
 1991 16.90839 
 1992 16.68493 
 1993 16.60126 
 1994 17.05832 
 1995 17.22449 
 1996  16.7175 
 1997 17.21499 
 1998 17.61638 
 1999 17.58109 
 2000 17.29787 
 2001 17.45382 
 2002 17.74327 
 2003 17.11524 
 2004 17.72089 
 2005 17.33447 
 2006 17.77015 
 2007 17.83629 
 2008 17.36057 
 2009 17.75217 
 2010 17.61854 
 2011 17.10426 
 2012   16.972 
 2013 17.64109 
 2014 17.33736 
 2015 17.84331 
 2016 17.98592 
 2017 17.92735 
 2018 17.63604 
 2019 8.835934