Year	% of land area
1990	37.24517641015763
1991	37.1970207711323
1992	37.14886513210697
1993	37.10070949308164
1994	37.052553854056306
1995	37.00439821503098
1996	36.95624257600565
1997	36.908086936980325
1998	36.85993129795499
1999	36.81177565892966
2000	36.76362001990433
2001	36.715464380879
2002	36.667308741853674
2003	36.61915310282834
2004	36.57099746380301
2005	36.52284182477768
2006	36.474686185752354
2007	36.42653054672702
2008	36.37837490770169
2009	36.33021926867636
2010	36.282063629651034
2011	36.2339079906257
2012	36.18575235160037
2013	36.137596712575046
2014	36.08944107354971
2015	36.04128543452438
2016	35.99312979549905
2017	35.94497415647373
2018	35.896818517448395
2019	35.84866287842306
2020	35.80050723939773
2021	35.75235160037241