Year	% of land area
1961	20.35663254320891
1962	20.748106245962926
1963	21.139579948716943
1964	21.531053651470963
1965	21.92252735422498
1966	22.314001056978995
1967	22.705474759733015
1968	23.09694846248703
1969	23.488422165241047
1970	24.075632719372074
1971	24.332047994675957
1972	25.73939595607665
1973	27.207422341404214
1974	28.624557145373757
1975	29.164790855174306
1976	29.681536142809605
1977	30.87357356769559
1978	31.52929201980857
1979	31.934467302158975
1980	32.32594100491299
1981	32.99144629959482
1982	33.664781068331735
1983	33.848773708626126
1984	34.06016950811329
1985	34.63172111413416
1986	34.86073323024526
1987	35.095617451897674
1988	34.70022901211611
1989	34.41249584059191
1990	34.24220477989391
1991	34.27352267611423
1992	33.741118440368766
1993	33.44164105776194
1994	33.427939478165555
1995	33.39270684491769
1996	33.713715281175986
1997	34.09148740433361
1998	34.428154788702074
1999	34.48296110708763
2000	34.59648848088629
2001	34.71980269725381
2002	34.80396954334593
2003	34.88030691538296
2004	35.06038481864981
2005	35.13476482217307
2006	35.14063692771438
2007	35.124977979604225
2008	34.91553954863082
2009	34.34594531112373
2010	34.30092583530701
2011	34.30875530936209
2012	34.120847932040164
2013	33.93346004032179
2014	33.35747421166983
2015	33.10105893636595
2016	33.01493472176006
2017	32.780050500107656
2018	32.77749907024995
2019	32.88379103133747
2020	33.220262091643995
2021	33.568870011156996