Year	% of land area
1990	16.73800655074162
1991	16.94954714669933
1992	17.161087742657045
1993	17.372628338614756
1994	17.58416893457247
1995	17.795728485850383
1996	18.007288487819324
1997	18.218829534427684
1998	18.430370581036044
1999	18.641911627644404
2000	18.85347275628394
2001	19.104968120561207
2002	19.356453899023084
2003	19.607938686774748
2004	19.859422866706524
2005	20.110908128425475
2006	20.362392776967077
2007	20.613877886082406
2008	20.865361693838402
2009	21.116845051735627
2010	21.36832885413419
2011	21.57462737043298
2012	21.780925886731776
2013	21.987224403030567
2014	22.193522919329357
2015	22.39982143562815
2016	22.63049793304581
2017	22.830706812054697
2018	23.030912176016514
2019	23.231117539978335
2020	23.431322903940153
2021	23.631528267901974