# year    value 
 1980 4.065171 
 1981 1.838379 
 1982 2.639734 
 1983 4.034453 
 1984 3.093829 
 1985 1.046521 
 1986  2.71157 
 1987 1.936472 
 1988 5.082541 
 1989    4.421 
 1990 5.216609 
 1991 2.264562 
 1992 3.130398 
 1993 3.374444 
 1994 4.892438 
 1995 5.167506 
 1996 2.575164 
 1997 3.439056 
 1998 5.234849 
 1999 3.124939 
 2000 4.002634 
 2001 5.378556 
 2002  3.65518 
 2003 2.736022 
 2004 3.732631 
 2005  2.75684 
 2006 2.255188 
 2007 6.526108 
 2008 4.670527 
 2009 3.179408 
 2010 2.954431 
 2011 3.110387 
 2012 3.341664 
 2013   3.3872 
 2014  5.94611 
 2015 4.747081 
 2016 5.949412 
 2017  3.28038 
 2018  4.38347