Year % of land area 1961 4.87268967299987 1962 5.001938735944164 1963 5.131187798888457 1964 5.260436861832752 1965 5.337986299599328 1966 5.518934987721339 1967 5.648184050665632 1968 5.777433113609926 1969 5.90668217655422 1970 6.035931239498513 1971 6.165180302442808 1972 6.242729740209383 1973 6.242729740209383 1974 6.371978803153677 1975 6.371978803153677 1976 6.371978803153677 1977 6.371978803153677 1978 6.371978803153677 1979 6.371978803153677 1980 6.475378053509112 1981 6.5787773038645465 1982 6.682176554219982 1983 6.785575804575417 1984 6.888975054930851 1985 6.992374305286287 1986 7.095773555641721 1987 7.212097712291586 1988 7.315496962647021 1989 7.418896213002456 1990 7.5222954633578905 1991 7.625694713713325 1992 7.729093964068761 1993 7.832493214424195 1994 8.013441902546207 1995 8.039291715135064 1996 8.788936280211969 1997 9.047434406100557 1998 8.788936280211969 1999 9.17668346904485 2000 9.305932531989143 2001 9.305932531989143 2002 9.435181594933436 2003 9.435181594933436 2004 9.822928783766317 2005 10.081426909654905 2006 10.59842316143208 2007 10.339925035543493 2008 10.986170350264961 2009 10.59842316143208 2010 10.339925035543493 2011 10.856921287320667 2012 10.339925035543493 2013 10.339925035543493 2014 10.339925035543493 2015 10.339925035543493 2016 10.339925035543493 2017 10.339925035543493 2018 10.339925035543493 2019 10.339925035543493 2020 10.339925035543493 2021 10.339925035543493