Year	% of land area
1990	37.47934938606283
1991	37.18607877531494
1992	36.89280816456705
1993	36.59953755381917
1994	36.30626694307128
1995	36.0129963323234
1996	35.71972572157551
1997	35.42645511082762
1998	35.133184500079736
1999	34.83991388933185
2000	34.54664327858396
2001	34.446499760803704
2002	34.34635624302344
2003	34.24621272524318
2004	34.14606920746293
2005	34.04592568968267
2006	33.94578217190241
2007	33.84563865412215
2008	33.745495136341894
2009	33.645351618561634
2010	33.54520810078137
2011	33.62557805772604
2012	33.7059480146707
2013	33.786317971615375
2014	33.86668792856003
2015	34.39516585074241
2016	34.344109996283905
2017	34.29305414182541
2018	34.25804991594465
2019	34.20671024903309
2020	34.15809893307469
2021	34.10701584222438