# year    value 
 1979 23.00862 
 1980 23.20192 
 1981 22.99397 
 1982 23.03836 
 1983 23.38409 
 1984 22.93451 
 1985 22.94392 
 1986 23.06435 
 1987 23.41897 
 1988 23.32014 
 1989 22.96677 
 1990 23.29916 
 1991  23.2333 
 1992 23.16601 
 1993 23.22414 
 1994  23.2435 
 1995 23.36279 
 1996 23.24592 
 1997 23.33499 
 1998 23.80626 
 1999 23.14555 
 2000 22.96589 
 2001 23.18617 
 2002 23.56919 
 2003 23.54903 
 2004 23.38714 
 2005 23.75944 
 2006 23.40015 
 2007 23.50864 
 2008 23.34664 
 2009  23.5869 
 2010  23.6598 
 2011 23.23362 
 2012 23.49245 
 2013 23.72418 
 2014 23.68413 
 2015 23.98225 
 2016  24.0278 
 2017 23.83496 
 2018 23.74309 
 2019 25.88476