Year	% of land area
1990	31.59561156473402
1991	31.4398312353685
1992	31.28405090600298
1993	31.12827057663747
1994	30.972490247271942
1995	30.81670991790643
1996	30.66092958854091
1997	30.50514925917539
1998	30.349368929809874
1999	30.193588600444354
2000	30.037808271078834
2001	29.897723339990993
2002	29.75763840890315
2003	29.617553477815303
2004	29.25739968981038
2005	29.118294497402495
2006	28.979267124736843
2007	28.84016102325406
2008	28.70117698083192
2009	28.562091707577817
2010	28.422070936825094
2011	28.261291343987203
2012	28.46793463190446
2013	28.303413710609746
2014	28.138905267802382
2015	27.97425104337541
2016	27.796600855863105
2017	27.624121047793086
2018	27.45278755513083
2019	27.278722731594204
2020	27.107788640082994
2021	26.934756968355934