Year	% of land area
1990	24.349410652614647
1991	24.233826453122386
1992	24.11824225363013
1993	24.002658054137868
1994	23.887073854645607
1995	23.771489655153353
1996	23.65590545566109
1997	23.54032125616883
1998	23.424737056676573
1999	23.30915285718432
2000	23.193568657692058
2001	23.082222742769805
2002	22.970876827847544
2003	22.8598310363294
2004	22.51733172253884
2005	22.407046541520483
2006	22.29675138190193
2007	22.186450555362736
2008	22.076292799429527
2009	21.96602905063903
2010	21.854801076878427
2011	21.716492422122325
2012	21.397245257578586
2013	21.260573009891292
2014	21.123913016079776
2015	20.9871090819235
2016	20.84305363387542
2017	20.704560710111586
2018	20.56882725767989
2019	20.428171972897644
2020	20.290282158528424
2021	20.150541691573974