Year % of land area 1961 20.8955223880597 1962 20.8955223880597 1963 19.402985074626866 1964 19.402985074626866 1965 19.402985074626866 1966 19.402985074626866 1967 19.402985074626866 1968 17.91044776119403 1969 17.91044776119403 1970 17.91044776119403 1971 14.925373134328357 1972 16.417910447761194 1973 16.417910447761194 1974 13.432835820895523 1975 11.940298507462686 1976 11.940298507462686 1977 11.940298507462686 1978 11.940298507462686 1979 11.940298507462686 1980 11.940298507462686 1981 10.44776119402985 1982 8.955223880597014 1983 8.955223880597014 1984 8.955223880597014 1985 7.462686567164178 1986 5.970149253731343 1987 4.477611940298507 1988 4.477611940298507 1989 2.9850746268656714 1990 2.9850746268656714 1991 1.791044776119403 1992 1.791044776119403 1993 1.791044776119403 1994 1.791044776119403 1995 1.791044776119403 1996 1.791044776119403 1997 1.791044776119403 1998 1.791044776119403 1999 1.791044776119403 2000 1.791044776119403 2001 1.791044776119403 2002 1.7777777777777777 2003 1.1644832605531297 2004 1.1611030478955007 2005 1.1030478955007257 2006 1.080691642651297 2007 1.1510791366906474 2008 1 2009 1 2010 1.0541310541310542 2011 1.0369318181818183 2012 1.0339943342776203 2013 0.9476661951909477 2014 0.9308885754583921 2015 0.9308885754583921 2016 0.9308885754583921 2017 0.9269662921348315 2018 0.9243697478991597 2019 0.9217877094972068 2020 0.9192200557103064 2021 0.9192200557103064