Year	% of land area
1990	22.77690812732567
1991	22.6587456692513
1992	22.540583211176926
1993	22.42242075310255
1994	22.304258295028177
1995	22.186095836953807
1996	22.067933378879435
1997	21.94977092080506
1998	21.831608462730685
1999	21.713446004656316
2000	21.595283546581943
2001	21.50315634472649
2002	21.41102914287104
2003	21.31890194101559
2004	21.22677473916014
2005	21.134647537304687
2006	21.042520335449236
2007	20.950393133593785
2008	20.858265931738337
2009	20.766138729882886
2010	20.674011528027435
2011	20.586055376098027
2012	20.49809922416862
2013	20.41014307223921
2014	20.3221869203098
2015	20.234230768380392
2016	20.152610156338095
2017	20.071327182398864
2018	19.98609959561254
2019	19.901214710063698
2020	19.816777405314063
2021	19.73203653242238