Year	% of land area
1990	30.977763369254923
1991	30.87416993295331
1992	31.218555595704224
1993	31.118759366651464
1994	31.12533111164056
1995	31.025192668611968
1996	30.925054225583384
1997	30.82491578255479
1998	30.724777339526206
1999	30.624638896497615
2000	30.524500453469027
2001	30.42640532057115
2002	30.32831018767327
2003	30.230065318038466
2004	30.15696092341036
2005	30.058635910268944
2006	30.12968062883431
2007	30.041905600466443
2008	29.95413143657993
2009	29.866505211508553
2010	29.778849657753483
2011	29.67829762758338
2012	29.577291294766518
2013	29.460660365053858
2014	29.361471247802264
2015	29.260455700140234
2016	29.15077785724165
2017	29.060598182527208
2018	28.94300639027017
2019	28.83372515663087
2020	28.724431254623973
2021	28.615118151863264