Year	% of land area
1990	80.37733515876872
1991	80.3504584198207
1992	80.32358190169147
1993	80.29670516274345
1994	80.26982842379543
1995	80.24295168484741
1996	80.21607516671818
1997	80.18919842777017
1998	80.16232168882216
1999	80.13544494987414
2000	80.1085684317449
2001	80.08668948460894
2002	80.06481053747295
2003	80.04293159033696
2004	80.02105264320099
2005	79.999173696065
2006	79.97729474892904
2007	79.95541580179305
2008	79.93353685465708
2009	79.91165790752109
2010	79.88977896038509
2011	79.82156163052599
2012	79.75334430066687
2013	79.68512697080776
2014	79.61690986176743
2015	79.5486925319083
2016	79.47241973236761
2017	79.39837919003666
2018	79.3243386477057
2019	79.25029810537474
2020	79.17625756304376
2021	79.1022170207128