Year	% of land area
1990	31.452575291088724
1991	31.31188672299272
1992	31.17119815489673
1993	31.030509586800733
1994	30.90044616628345
1995	30.759709205650715
1996	30.61897224998647
1997	30.478235289353734
1998	30.33749832872099
1999	30.196761368088257
2000	30.05550174985024
2001	29.90261046384558
2002	29.74971917784092
2003	29.59682789183626
2004	29.230771677792298
2005	29.079008547818628
2006	28.927078272871768
2007	28.775157685805322
2008	28.623724478402824
2009	28.471908144002487
2010	28.319218604109125
2011	28.125165245081345
2012	27.76204514339804
2013	27.569749652647086
2014	27.377370316809262
2015	27.184856134790184
2016	26.99231179268841
2017	26.803496449589556
2018	26.616661291703693
2019	26.42621782664021
2020	26.237825174178656
2021	26.048045610423447