Year	% of land area
1990	34.85010535069993
1991	34.76046384734163
1992	31.897612630653846
1993	31.826129922620428
1994	31.754647237473595
1995	31.68316455232676
1996	31.61168189006653
1997	31.5401992049197
1998	31.46871649688628
1999	31.39723381173945
2000	31.25018916947398
2001	31.17457782528795
2002	31.098581194329252
2003	31.022825386366232
2004	30.94699774397276
2005	30.871028300484568
2006	30.79502356261217
2007	30.718086057524808
2008	30.642209625389594
2009	30.56636749799939
2010	30.490740416022234
2011	30.419683367585435
2012	30.34811085970268
2013	30.276551883334218
2014	30.204916708887406
2015	30.10021755839227
2016	30.030892009485097
2017	29.969802201270916
2018	29.902628703424313
2019	29.828991737987582
2020	29.754491837377014
2021	29.68061792313729