Year	% of land area
1961	28.65648936513536
1962	28.858414357428938
1963	29.0378543981144
1964	29.250846593760745
1965	29.432401032271276
1966	29.60120787757859
1967	29.750489928232888
1968	29.949849822112373
1969	30.081103849205597
1970	30.31880111417637
1971	30.630335376880282
1972	30.938080416113493
1973	31.190368289151696
1974	31.437698461274802
1975	31.708965836895356
1976	32.03131617765299
1977	32.40062194905489
1978	32.73593018875588
1979	33.05811236881597
1980	33.39100060149489
1981	33.56755491492547
1982	33.71601580579449
1983	33.997629075183525
1984	34.196396299999606
1985	34.33229351503932
1986	34.32564511578915
1987	34.34132419573011
1988	34.32585351902332
1989	34.32802150469428
1990	34.46006285927635
1991	34.46687631629172
1992	34.418809290508676
1993	34.38887158223203
1994	34.32208187341454
1995	34.273129871148775
1996	34.315615107815596
1997	34.36548020269432
1998	34.4949259923281
1999	34.536638799425525
2000	34.50021818595239
2001	34.35742091386197
2002	34.37748127340824
2003	34.3977559313381
2004	34.45316963932402
2005	34.52372111946808
2006	34.52353699942706
2007	34.598796151027315
2008	34.31331172721674
2009	34.180756251236595
2010	34.30058771238042
2011	34.23129506629178
2012	34.27793171569498
2013	34.28984745457556
2014	34.079646622664505
2015	34.12479184352827
2016	34.0112547679633
2017	33.83511500400506
2018	33.803336211476044
2019	33.8506546200851
2020	34.03185839859466
2021	34.04437825543643