Year	% of land area
1961	36.4657950097196
1962	36.75871435038479
1963	37.06228530343781
1964	37.36585625649083
1965	37.77061752722818
1966	38.15407557318989
1967	38.537533619151596
1968	38.920991665113306
1969	39.41096583495327
1970	39.90094000479323
1971	40.3962399808271
1972	40.88834447314462
1973	41.48589992810162
1974	42.19103666817565
1975	42.68207599925439
1976	43.30981101909301
1977	43.937546049583254
1978	44.57380235933214
1979	45.06031475514606
1980	45.5467206348361
1981	46.11178867201022
1982	47.13530210635635
1983	48.24413495592895
1984	49.48068063803158
1985	50.73863606103374
1986	51.38934306180598
1987	51.954943679599495
1988	52.55239261843262
1989	53.20320613532874
1990	53.86456474848881
1991	54.47010891273667
1992	54.78273373631934
1993	55.19910526455942
1994	55.690144595638166
1995	55.69020391468476
1996	55.69441737153862
1997	55.69444400062632
1998	55.69447062971401
1999	55.69449725880171
2000	55.694583211727036
2001	55.757871864491534
2002	55.82113206589726
2003	55.8843892938216
2004	55.94764475133046
2005	56.010903183926885
2006	56.07415984476021
2007	56.13741769624517
2008	56.200671974685534
2009	56.26392504386618
2010	56.18347308129312
2011	56.103660218118236
2012	56.02352780524426
2013	55.943395392370284
2014	55.86326297949631
2015	55.78313056662233
2016	55.70300408704109
2017	55.62287166563168
2018	55.542739244222275
2019	55.46264942944396
2020	55.46264942944396
2021	55.46264942944396