Year	% of land area
1990	3.731767184166285
1991	3.713698175743867
1992	3.6956237371368226
1993	3.6775547552641603
1994	3.659485773391498
1995	3.6414167988656003
1996	3.6233478169929376
1997	3.605278835120275
1998	3.587209853247612
1999	3.5691408713749495
2000	3.551071889502287
2001	3.5366592241477033
2002	3.52224655879312
2003	3.507880282275303
2004	3.4934699929271695
2005	3.4790545703697626
2006	3.4646264419349464
2007	3.4502085798956768
2008	3.4357932844383225
2009	3.422011559993654
2010	3.4075981442333405
2011	3.389776401024393
2012	2.956405437181809
2013	2.937936996813667
2014	2.919451746953556
2015	2.900938038527913
2016	2.883323261220978
2017	2.86394290918001
2018	2.8444204691597164
2019	2.8266207876558407
2020	2.8088952608016657
2021	2.791120844538008