Year	% of land area
1990	28.941966736299847
1991	28.961097621483308
1992	29.075265560947688
1993	29.11962927609845
1994	29.138786965681387
1995	29.158002433247447
1996	29.177202474781936
1997	29.139720618983834
1998	29.158908124512763
1999	29.178087420843617
2000	29.188276916514837
2001	29.211633655234728
2002	29.23421049149403
2003	29.25691120810699
2004	29.28024132963544
2005	29.303498910776963
2006	29.327158367289186
2007	29.350291450059476
2008	29.38586847690184
2009	29.40815611529233
2010	29.430121648321666
2011	29.471062615705975
2012	29.512085271644366
2013	29.55217910023882
2014	29.593094920965342
2015	29.634778519031165
2016	29.660472402148454
2017	29.660400576747808
2018	29.667152400700893
2019	29.67501074245963
2020	29.683941676373124
2021	29.840878601386684