Year	% of land area
1990	25.80582095134473
1991	26.0708578423039
1992	26.335894733263064
1993	26.60093162422223
1994	26.865968515181393
1995	27.131005406140556
1996	27.396042297099726
1997	27.661079188058892
1998	27.926116079018055
1999	28.191152969977217
2000	28.301456116976308
2001	28.524232545871403
2002	28.7470089747665
2003	28.969785403661596
2004	29.192561832556695
2005	29.41533826145179
2006	29.638114690346885
2007	29.860891119241977
2008	30.08366754813708
2009	30.30644397703217
2010	30.529220405927266
2011	30.71117754076519
2012	30.893134675603108
2013	31.07509181044103
2014	31.25704894527895
2015	31.439006080116872
2016	31.62096997815486
2017	31.802933876192856
2018	31.98489777423086
2019	32.16697044809734
2020	32.34893496146653
2021	32.530899474835735