Year	% of land area
1990	20.231527093596057
1991	20.273891625615764
1992	20.31625615763547
1993	20.358620689655172
1994	20.400985221674876
1995	20.44334975369458
1996	20.485714285714288
1997	20.52807881773399
1998	20.570443349753695
1999	20.6128078817734
2000	20.655172413793103
2001	20.4807881773399
2002	20.3064039408867
2003	20.1320197044335
2004	19.957635467980296
2005	19.783251231527093
2006	19.608866995073893
2007	19.43448275862069
2008	19.26009852216749
2009	19.085714285714285
2010	18.911330049261082
2011	19.214822233350027
2012	19.205808713069604
2013	19.196795192789185
2014	19.187781672508763
2015	19.178768152228344
2016	19.17376064096144
2017	19.354031046569855
2018	19.374061091637454
2019	19.394091136705057
2020	19.414121181772657
2021	19.434151226840264