# year    value 
 1980 5.638092 
 1981 5.650061 
 1982 5.492137 
 1983 5.302865 
 1984  5.50049 
 1985  5.56962 
 1986 5.589065 
 1987 5.648322 
 1988 5.724006 
 1989 5.779665 
 1990 5.807721 
 1991 5.768171 
 1992  5.35747 
 1993 5.563303 
 1994 5.673347 
 1995 5.730391 
 1996 5.842858 
 1997 5.931332 
 1998 5.991684 
 1999 6.000216 
 2000 6.048938 
 2001 6.130764 
 2002   6.1488 
 2003 6.133692 
 2004   6.1479 
 2005 6.197764