Year	% of land area
1990	36.23000572826162
1991	36.078752472873454
1992	35.92749921748529
1993	35.77624596209712
1994	35.62499270670896
1995	35.47373945132079
1996	35.322486195932626
1997	35.17123294054446
1998	35.019979685156294
1999	34.86872642976813
2000	34.71747317437996
2001	34.53746250843507
2002	34.357451842490164
2003	34.17744117654527
2004	33.65427357736277
2005	33.47597714603286
2006	33.29780171944035
2007	33.119504037460835
2008	32.94139587722355
2009	32.76313062589215
2010	32.5834154809305
2011	32.37099351849684
2012	31.890654257453274
2013	31.680635048113388
2014	31.470633939390307
2015	31.26041983120001
2016	31.039681540557375
2017	30.824316220010562
2018	30.611511759897468
2019	30.391625948267823
2020	30.1742527100624
2021	29.95519405973367