Year	% of land area
1990	57.40411925919774
1991	57.02430030728345
1992	56.644481355369145
1993	56.26466240345486
1994	55.88484345154057
1995	55.50502449962627
1996	55.12520554771198
1997	54.74538659579768
1998	54.365567643883395
1999	53.98574869196911
2000	53.60592974005481
2001	53.429615480441825
2002	53.25330122082884
2003	53.076986961215844
2004	52.90067270160286
2005	52.72435844198987
2006	52.54804418237688
2007	52.37172992276389
2008	52.195415663150904
2009	52.01910140353792
2010	51.84278714392493
2011	51.66647288431193
2012	51.49015862469894
2013	51.313844365085956
2014	51.13753010547296
2015	50.961215845859975
2016	50.78490158624699
2017	50.608587326634
2018	50.432273067021015
2019	50.25595880740802
2020	50.079644547795034
2021	49.90333028818205