Year	% of land area
1990	51.433497536945815
1991	51.79901477832512
1992	52.164532019704424
1993	52.53004926108375
1994	52.895566502463055
1995	53.26108374384236
1996	53.62660098522167
1997	53.992118226600994
1998	54.357635467980295
1999	54.7231527093596
2000	55.088669950738925
2001	55.45413245758073
2002	55.81959496442255
2003	56.185057471264365
2004	56.55051997810618
2005	56.915982484948
2006	57.28144499178982
2007	57.64690749863164
2008	58.01237000547346
2009	58.377832512315265
2010	58.74329501915708
2011	59.10870279146141
2012	59.474110563765734
2013	59.839518336070064
2014	60.20492610837439
2015	60.57033388067872
2016	60.93596059113301
2017	61.301587301587304
2018	61.667214012041605
2019	62.0328407224959
2020	62.3984674329502
2021	62.76409414340449