Year	% of land area
1961	35.88948703313998
1962	36.09795628444864
1963	36.319190457447625
1964	36.54512216719279
1965	36.807775413347855
1966	37.060832977207035
1967	37.324000718495434
1968	37.57375678037363
1969	37.871672877474516
1970	38.20046690943415
1971	38.444885005199716
1972	38.8119453246399
1973	39.2080392588797
1974	39.70754779364764
1975	40.0516517022403
1976	39.53112985348902
1977	39.999775786426866
1978	40.422106761884265
1979	40.67923618715066
1980	40.9998254363127
1981	41.36970651103202
1982	42.0189992703305
1983	42.72190930938683
1984	43.394622172424214
1985	44.3707528326443
1986	44.91275091272713
1987	45.49039364648197
1988	45.96551014248442
1989	46.43508296931392
1990	46.89241669091453
1991	47.07259370551586
1992	47.092792211852235
1993	47.103492611042334
1994	47.36620607832535
1995	47.43396310302418
1996	47.49058317834212
1997	48.22056837230821
1998	48.278686610474495
1999	48.511403185783145
2000	48.499133976617856
2001	48.67497946176013
2002	48.80913805943986
2003	47.935511864177705
2004	48.070335178154316
2005	48.137525659776664
2006	48.329608431643486
2007	48.47995457791023
2008	48.58401824020739
2009	48.68738517911411
2010	48.695328279479575
2011	48.74183283630765
2012	48.7270357804232
2013	48.74024093970462
2014	48.70239893118642
2015	48.810026149498015
2016	48.883941933887684
2017	49.08355626465772
2018	49.07185987855859
2019	49.054958771394745
2020	49.043277617942216
2021	49.032136001402925