Year	% of land area
1990	70.14598860149057
1991	69.52902235861464
1992	68.91205611573871
1993	68.29508987286277
1994	67.67812362998684
1995	67.06115738711091
1996	66.44419114423499
1997	65.82722490135906
1998	65.21025865848313
1999	64.59329241560718
2000	63.976326172731255
2001	63.6786058746164
2002	63.380885576501534
2003	63.08316527838668
2004	62.78544498027181
2005	62.48772468215695
2006	62.19000438404208
2007	61.892284085927216
2008	61.59456378781236
2009	61.296843489697494
2010	60.99912319158264
2011	60.485664182376155
2012	59.972205173169655
2013	59.458746163963184
2014	58.945287154756684
2015	58.43182814555019
2016	57.94300745287154
2017	57.453748355984224
2018	56.96492766330557
2019	56.475668566418236
2020	55.986409469530905
2021	55.497150372643574