Year	% of land area
1961	14.76452928260967
1962	14.76452928260967
1963	14.898955952861048
1964	15.01097817807053
1965	15.235022628489492
1966	15.459067078908456
1967	15.459067078908456
1968	15.683111529327418
1969	15.683111529327418
1970	15.853385311645832
1971	15.916117757763141
1972	15.97660975937626
1973	16.121442975576965
1974	16.13264620210621
1975	16.341026215550077
1976	16.390320412278736
1977	16.692807528568228
1978	17.158861752184627
1979	16.813802375084023
1980	16.872059153036073
1981	17.23056240197177
1982	17.403092090522073
1983	17.52856822764956
1984	17.55321532601389
1985	17.651803719471207
1986	17.828814698633206
1987	18.297109567555456
1988	18.315034730002242
1989	18.949137351557248
1990	19.509298678019267
1991	19.53170513107775
1992	20.017925162446783
1993	20.16356710732691
1994	20.44364777055792
1995	19.98879677347076
1996	20.380909701994174
1997	20.120994846515796
1998	20.239749047725745
1999	19.75801030696841
2000	19.643737396370152
2001	19.018597356038537
2002	18.825901859735602
2003	20.2890432444544
2004	18.39569796101277
2005	18.19852117409814
2006	18.06856374635895
2007	18.0708043916648
2008	18.041676002688774
2009	18.01389200089626
2010	17.318619762491597
2011	17.48554783777728
2012	18.030472776159534
2013	18.21196504593323
2014	17.031369034281873
2015	16.798790051534844
2016	18.420345059377098
2017	18.863453282545372
2018	17.59393053999552
2019	15.458131301814923
2020	17.082679811785795
2021	16.831727537530806