Year	% of land area
1990	12.290589289715438
1991	12.295350660990366
1992	12.300112032265293
1993	12.30487340354022
1994	12.309634774815146
1995	12.314396146090074
1996	12.319157517365001
1997	12.323918888639929
1998	12.328680259914854
1999	12.333441631189784
2000	12.338203002464711
2001	12.375852565538874
2002	12.413502128613041
2003	12.451151691687205
2004	12.488801254761372
2005	12.526450817835538
2006	12.564100380909702
2007	12.601749943983867
2008	12.639399507058032
2009	12.677049070132199
2010	12.714698633206362
2011	12.719233699305402
2012	12.723768765404436
2013	12.728303831503474
2014	12.73283889760251
2015	12.737373963701545
2016	12.771207707819855
2017	12.79764732242886
2018	12.820053775487342
2019	12.843580551198746
2020	12.866883262379567
2021	12.890335424602286