Year | Value | 2022 | 15.240471931147 | 2021 | 13.945954699126 | 2020 | 13.239962513874 | 2019 | 14.398957807425 | 2018 | 15.706429737781 | 2017 | 16.291706196726 | 2016 | 16.454713337464 | 2015 | 14.315693934302 | 2014 | 16.30627740681 | 2013 | 15.321202274713 | 2012 | 15.114444634441 | 2011 | 15.520998444111 | 2010 | 15.298204013808 | 2009 | 16.141050285621 | 2008 | 17.516534906088 | 2007 | 18.885963008424 | 2006 | 19.320321961151 | 2005 | 16.870375169181 | 2004 | 16.917477451102 | 2003 | 14.190985594231 | 2002 | 11.911756137449 | 2001 | 12.157824861927 | 2000 | 14.381484724281 | 1999 | 16.542379206438 | 1998 | 17.335486835385 | 1997 | 17.558221150989 | 1996 | 16.40313792747 | 1995 | 19.685051116413 | 1994 | 18.038084644412 | 1993 | 16.082269783436 | 1992 | 11.066106478854 | 1991 | 15.419138850184 | 1990 | 16.186768646358 | 1989 | 17.785848012525 | 1988 | 19.717953632397 | 1987 | 18.941357440733 | 1986 | 23.873318251475 | 1985 | 23.332844346715 | 1984 | 24.763383315853 | 1983 | 21.355787395286 | 1982 | 23.346979928548 | 1981 | 9.5109420330666 | 1980 | 5.2280347713977 | 1979 | 15.571023178962 | 1978 | 18.25194660039 | 1977 | 4.1018438397059 |
|