Year	% of land area
1961	29.901381183165938
1962	30.05470160986448
1963	31.04738640645505
1964	30.955134285305924
1965	30.977222821355717
1966	31.183815599703752
1967	30.97072619310578
1968	31.303353559502618
1969	32.78328547483856
1970	32.21418084014396
1971	32.45455608539169
1972	33.22765484713434
1973	33.188675077634706
1974	32.69233267933942
1975	32.363603289892545
1976	32.303834309993114
1977	32.56499876564064
1978	32.64295830463989
1979	33.4940166053818
1980	32.94310252978704
1981	33.110715538635446
1982	31.442381404051297
1983	30.78882060210751
1984	31.836077075997558
1985	31.956914361446408
1986	31.908839312396864
1987	32.43636552629185
1988	32.20508556059405
1989	32.327222171692895
1990	32.02447929524577
1991	32.04916648259553
1992	31.85166898379741
1993	31.808791237347815
1994	32.09984018294505
1995	32.03357457479568
1996	31.85166898379741
1997	31.569715317750084
1998	31.754219560048334
1999	31.54632745605031
2000	30.957732936605904
2001	30.92524979535621
2002	31.176019645803827
2003	30.367839091511506
2004	31.016202590855347
2005	30.962930239205853
2006	29.859802762366332
2007	28.5578784610787
2008	28.006964385483933
2009	27.74190195288645
2010	27.784779699336042
2011	26.686849525096473
2012	26.73622389979601
2013	26.732325922846044
2014	26.894741629094497
2015	26.8310746722451
2016	26.48285539804841
2017	25.98391434845315
2018	25.626599794706546
2019	25.440796226758312
2020	25.448592180658235
2021	25.831893247404597