Year	% of land area
1961	16.43197210487494
1962	16.361563736337423
1963	16.294508147254074
1964	16.227452558170725
1965	16.160396969087373
1966	16.093341380004023
1967	15.959230201837324
1968	15.8586468182123
1969	15.758063434587271
1970	15.657480050962247
1971	15.570307785153892
1972	15.758063434587271
1973	15.92730442946719
1974	16.097119286361046
1975	16.26588858704766
1976	16.7689573062347
1977	17.10433645235939
1978	17.272026025421738
1979	17.43971559848409
1980	17.533621759399
1981	17.506791427709025
1982	17.573867256933966
1983	17.640943086158902
1984	17.708018915383843
1985	17.942784317671126
1986	18.110473890733473
1987	18.177549719958414
1988	18.24462554918335
1989	18.31170137840829
1990	18.378777207633227
1991	18.40225374786196
1992	18.227856591877117
1993	18.06016701881477
1994	17.892477445752423
1995	17.724787872690076
1996	17.55709829962773
1997	17.389408726565385
1998	17.221719153503035
1999	17.054029580440687
2000	16.882986215917096
2001	16.715296642854746
2002	16.550960861253646
2003	16.66834356239729
2004	17.17141228158433
2005	16.785726263540933
2006	17.28879498272797
2007	17.74155682999631
2008	18.27816346379582
2009	18.445853036858168
2010	17.77509474460878
2011	18.27816346379582
2012	18.714156353757925
2013	18.74769426837039
2014	18.74769426837039
2015	18.74769426837039
2016	18.74769426837039
2017	18.74769426837039
2018	18.74769426837039
2019	18.74769426837039
2020	18.74769426837039
2021	18.74769426837039