Year	% of land area
1990	29.12490529991107
1991	28.945600974999174
1992	28.766296650087288
1993	28.5869923251754
1994	28.407688000263516
1995	28.228383675351626
1996	28.049079350439737
1997	27.869775025527847
1998	27.69047070061596
1999	27.51116637570408
2000	27.33186205079219
2001	27.152556627908254
2002	26.97325120502432
2003	26.793945782140387
2004	26.61464035925645
2005	26.435334936372524
2006	26.25602951348859
2007	26.076724090604653
2008	25.89741866772072
2009	25.718113244836783
2010	25.53880782195285
2011	25.359502399068916
2012	25.180196976184988
2013	25.000891553301052
2014	24.82158613041712
2015	24.64228070753319
2016	24.46297956674023
2017	24.283683037429867
2018	24.104384202378206
2019	23.92508536732655
2020	23.745786532274888
2021	23.56648769722323