Year	% of land area
1961	52.055241764340984
1962	51.67978060008489
1963	51.36635214992328
1964	51.2618759998694
1965	50.39994776192497
1966	50.39668288223579
1967	49.92327532730419
1968	49.83838845538542
1969	49.31274282542688
1970	49.260504750399946
1971	48.907897743968135
1972	48.46387410623919
1973	48.32021939991512
1974	48.20268373110451
1975	48.258186685820625
1976	48.199418851415324
1977	48.12106173887492
1978	48.02311534819942
1979	47.83701720591596
1980	47.73580593555128
1981	47.379934049430275
1982	47.28851741813314
1983	47.25586862124131
1984	47.4550262822815
1985	47.37666916974109
1986	47.28851741813314
1987	47.27545789937641
1988	47.22321982434947
1989	47.0599758398903
1990	46.97508896797153
1991	46.883672336674394
1992	46.808580103823175
1993	46.704103953769305
1994	46.68777955532339
1995	46.39394038329688
1996	45.721375167325085
1997	45.72790492670345
1998	45.89441379085181
1999	45.94338698618956
2000	45.68546149074407
2001	44.35012569786803
2002	42.476084756276734
2003	41.10175026123302
2004	41.164756961446805
2005	39.63372833219078
2006	40.376077304779315
2007	38.59689213893967
2008	39.31766242246164
2009	39.39532453963693
2010	35.35653650254669
2011	36.24073408875682
2012	35.676964274051336
2013	35.243786943600796
2014	35.69025768313792
2015	35.556353897906526
2016	35.291812273425
2017	35.621672817531596
2018	35.95714798967894
2019	36.11446865505864
2020	36.42243491327214
2021	36.19327017314603