Year	% of land area
1990	26.36394516825369
1991	26.519542849629087
1992	26.67514053100448
1993	26.830738212379877
1994	26.986335893755275
1995	27.14193357513067
1996	27.297531256506062
1997	27.45312893788146
1998	27.608726619256856
1999	27.764324300632254
2000	27.919870992956113
2001	28.12642105897543
2002	28.33297112499475
2003	28.52389357271016
2004	28.746071257033385
2005	28.95315008300506
2006	29.159703921235597
2007	29.366257759466137
2008	29.57281159769668
2009	29.779365435927218
2010	29.98591927415776
2011	30.138232184046593
2012	30.290545093935428
2013	30.44285800382426
2014	30.595170913713094
2015	30.74748382360193
2016	30.89979673349076
2017	31.052109643379595
2018	31.20442255326843
2019	31.35673546315726
2020	31.509048373046095
2021	31.66136128293493