Year | Value | 2022 | 22.638263807758 | 2021 | 23.569271673914 | 2020 | 20.847884852453 | 2019 | 23.769600975151 | 2018 | 23.156919843663 | 2017 | 22.752944566294 | 2016 | 22.006075649568 | 2015 | 22.254869262576 | 2014 | 21.488940536257 | 2013 | 21.389821829011 | 2012 | 21.455713942165 | 2011 | 22.115343356068 | 2010 | 21.086119511151 | 2009 | 20.971933575945 | 2008 | 23.440962927269 | 2007 | 23.748717415311 | 2006 | 23.307757403568 | 2005 | 22.464069386194 | 2004 | 22.552434367671 | 2003 | 22.238346216842 | 2002 | 22.752387569429 | 2001 | 23.940476264303 | 2000 | 23.838600952845 | 1999 | 24.493878048134 | 1998 | 23.85633165708 | 1997 | 22.798806004823 | 1996 | 21.762576348007 | 1995 | 21.875219981755 | 1994 | 21.35331178951 | 1993 | 21.237205985938 | 1992 | 22.378675114987 | 1991 | 22.960770589291 | 1990 | 23.327394253897 | 1989 | 23.215772239745 | 1988 | 22.686890989716 | 1987 | 21.379740814248 | 1986 | 21.470063221806 | 1985 | 20.193659256184 | 1984 | 20.175505118592 | 1983 | 20.388371695564 | 1982 | 20.795782899204 | 1981 | 21.995019016593 | 1980 | 24.353321399643 | 1979 | 25.039876217624 | 1978 | 25.032353273509 | 1977 | 24.95332262111 | 1976 | 25.160132414894 | 1975 | 25.397236195615 |
|