Year	% of land area
1990	41.83931403971435
1991	41.77117291974863
1992	41.85887542918343
1993	41.77114340157781
1994	41.79940102840472
1995	41.711424874725225
1996	41.623448721045726
1997	41.53547256736621
1998	41.447496413686714
1999	41.35952026000721
2000	41.27154410632771
2001	41.18932422161225
2002	41.1071043368968
2003	41.02471955725639
2004	40.970050050919696
2005	40.887610717707354
2006	40.88445206838504
2007	40.810497820171555
2008	40.7365441636517
2009	40.662753765579566
2010	40.58893089308931
2011	40.49770494478986
2012	40.40597585734431
2013	40.296885202964646
2014	40.207157555966646
2015	40.11540001111692
2016	40.01708707208841
2017	39.94027885335399
2018	39.83280717736988
2019	39.734556061759754
2020	39.63629754136418
2021	39.538012659675644