# year    value 
 1980 2.808074 
 1981 2.812765 
 1982 2.650465 
 1983 2.581061 
 1984 2.691987 
 1985 2.700844 
 1986 2.757785 
 1987 2.840751 
 1988 2.899625 
 1989 2.929402 
 1990 2.985345 
 1991 2.904018 
 1992 2.598229 
 1993 2.774306 
 1994 2.763573 
 1995 2.866956 
 1996  2.98875 
 1997   3.0918 
 1998 3.080535 
 1999  3.14319 
 2000 3.117753 
 2001 3.217729 
 2002 3.282792 
 2003 3.207276 
 2004 3.269151 
 2005  3.32329