Year % of land area 1961 14.325248250040698 1962 14.32117857724239 1963 14.223506430083022 1964 14.125834282923652 1965 14.032231808562592 1966 13.934559661403224 1967 13.836887514243854 1968 13.739215367084487 1969 13.641543219925117 1970 13.547940745564057 1971 13.450268598404689 1972 13.352596451245319 1973 13.254924304085952 1974 13.161321829724889 1975 13.063649682565522 1976 12.965977535406154 1977 12.868305388246783 1978 12.770633241087417 1979 12.677030766726356 1980 12.579358619566989 1981 12.481686472407619 1982 12.38401432524825 1983 12.286342178088882 1984 12.19273970372782 1985 12.095067556568452 1986 11.997395409409084 1987 11.899723262249715 1988 11.806120787888654 1989 11.708448640729285 1990 11.610776493569917 1991 11.513104346410548 1992 11.41543219925118 1993 11.321829724890119 1994 11.22415757773075 1995 11.126485430571382 1996 11.130555103369689 1997 11.134624776167996 1998 11.138694448966303 1999 11.14276412176461 2000 11.146833794562918 2001 11.150903467361225 2002 11.154973140159532 2003 11.159042812957837 2004 11.163112485756145 2005 11.154973140159532 2006 11.191600195344293 2007 11.395083835259644 2008 11.598567475174997 2009 11.598567475174997 2010 11.802051115090347 2011 11.802051115090347 2012 12.209018394921047 2013 12.615985674751752 2014 12.615985674751752 2015 12.615985674751752 2016 12.615985674751752 2017 12.615985674751752 2018 12.615985674751752 2019 12.615985674751752 2020 12.615985674751752 2021 12.615985674751752