Year	% of land area
1990	2.2112981944727435
1991	2.2147087724822643
1992	2.218119350491785
1993	2.221529928501306
1994	2.2249405065108268
1995	2.2283510960972084
1996	2.2317616741067297
1997	2.2351722521162505
1998	2.238582830125771
1999	2.2419934081352917
2000	2.2454039861448125
2001	2.2681586539352065
2002	2.2909133217256006
2003	2.313718882160012
2004	2.33647946041254
2005	2.3592346814144025
2006	2.381973356549202
2007	2.40472563552209
2008	2.427480672117141
2009	2.4509479147727866
2010	2.473712430198975
2011	2.4753691261178012
2012	2.4770258220366266
2013	2.4787376312496905
2014	2.480394364005009
2015	2.482050809321848
2016	2.4848174345798513
2017	2.487715280289551
2018	2.48952317753238
2019	2.493938049256544
2020	2.497534136463339
2021	2.5016787689352302