Year	% of land area
1961	49.99050548782804
1962	50.31331890167483
1963	50.465231096426265
1964	50.571569632752265
1965	50.328510121149975
1966	50.25635182864304
1967	50.309521096806044
1968	50.31331890167483
1969	49.71706353727545
1970	49.7056701226691
1971	49.69807451293153
1972	51.21643689947211
1973	51.200676009266644
1974	51.18491511906118
1975	52.954692187915384
1976	54.51179218411758
1977	54.21822186776043
1978	55.06019520717026
1979	54.851695719873916
1980	55.41377084045421
1981	57.679161444684965
1982	55.523907181649
1983	55.41566974288861
1984	54.965629865937494
1985	54.66180547643462
1986	54.64661425695948
1987	54.2098666970491
1988	53.89085108807109
1989	53.55094755231477
1990	52.85405035889256
1991	52.25241464433557
1992	51.654908283012425
1993	51.05592077779044
1994	50.4568451634955
1995	49.85782841517603
1996	49.25878812046637
1997	48.659988986365875
1998	48.06121947514336
1999	47.46247730811591
2000	46.863819832137025
2001	46.26516767308496
2002	45.666341954350386
2003	45.03437013406251
2004	45.15589988986366
2005	44.47989062321978
2006	43.200030382438946
2007	43.625384527742966
2008	43.196232577570164
2009	43.63677794234932
2010	43.325357943108884
2011	43.184839162963804
2012	42.571113896168015
2013	42.178420872735565
2014	42.21639892142341
2015	40.68208575443394
2016	40.309900877292925
2017	40.4238350233565
2018	39.86935551251376
2019	39.28829136758954
2020	38.562910637651434
2021	38.64266453989594