Year	% of land area
1990	24.750134336378295
1991	24.514777001612035
1992	24.27941966684578
1993	24.044062332079527
1994	23.80870499731327
1995	23.573347662547018
1996	23.337990327780762
1997	23.102632993014506
1998	22.867275658248253
1999	22.631918323482
2000	22.396560988715745
2001	22.161203653949492
2002	21.925846319183236
2003	21.69048898441698
2004	21.455131649650724
2005	21.21977431488447
2006	20.984416980118215
2007	20.74905964535196
2008	20.513702310585707
2009	20.27834497581945
2010	20.042987641053198
2011	19.807630306286946
2012	19.57227297152069
2013	19.336915636754433
2014	19.10155830198818
2015	18.866200967221925
2016	18.62976894142934
2017	18.393336915636755
2018	18.162278344975817
2019	17.925846319183236
2020	17.689414293390648
2021	17.452982267598067