Year	% of land area
1961	40.084849443408125
1962	40.09415311044848
1963	40.104387144192884
1964	40.11787746140141
1965	40.12764631179379
1966	40.13788034553819
1967	40.147184012578556
1968	40.16393061325122
1969	40.18021203057185
1970	40.20114528141267
1971	40.223008898957524
1972	40.246268066558436
1973	40.270922784215394
1974	40.30348561885667
1975	40.32395368634547
1976	40.35465578757867
1977	40.37977568858766
1978	40.4039652228926
1979	40.42861994054957
1980	40.45327465820653
1981	40.47699900915946
1982	40.50258409352046
1983	40.596551130628136
1984	42.99364094357791
1985	45.41352474077658
1986	47.811544920430386
1987	50.23049835092501
1988	52.62619261381873
1989	55.02653871023264
1990	57.4413054905591
1991	57.53015551079458
1992	57.56457907884393
1993	60.839004693700026
1994	64.09528815782741
1995	67.3515716219548
1996	70.60785508608218
1997	73.86413855020957
1998	77.58560536635515
1999	80.84188883048253
2000	80.84188883048253
2001	80.84467993059464
2002	80.84561029729868
2003	80.84793621405876
2004	80.80653489572916
2005	80.8102563625453
2006	80.79025347840852
2007	80.79071866176054
2008	80.74280477650267
2009	80.67907465727616
2010	80.66558434006764
2011	80.65721103973131
2012	80.63720815559454
2013	80.61394898799362
2014	80.74433988156431
2015	80.77304169438383
2016	80.76838986086365
2017	80.7540156952863
2018	80.75373658527508
2019	80.76347519874959
2020	80.77321381222409
2021	80.77304169438383