# year    value 
 1979 -6.386786 
 1980 -4.632098 
 1981 -3.858273 
 1982 -4.977986 
 1983 -3.273989 
 1984 -4.908149 
 1985 -6.259917 
 1986 -4.743602 
 1987 -4.144124 
 1988 -4.425096 
 1989 -3.77691 
 1990 -3.754399 
 1991 -4.287053 
 1992 -3.625252 
 1993 -4.228846 
 1994 -5.159484 
 1995 -3.189019 
 1996 -5.198872 
 1997 -4.073784 
 1998 -3.451404 
 1999 -2.856445 
 2000 -3.041524 
 2001 -4.396102 
 2002 -2.491184 
 2003 -4.850351 
 2004 -3.180523 
 2005 -4.417851 
 2006 -4.236473 
 2007 -2.359282 
 2008 -4.364141 
 2009 -4.064602 
 2010 -4.755792 
 2011 -4.698495 
 2012 -4.328076 
 2013  -4.2642 
 2014 -4.446132 
 2015 -3.334069 
 2016 -1.992862 
 2017 -3.040544 
 2018 -3.96227 
 2019 -3.721717