Year	% of land area
1990	90.35
1991	90.18
1992	90.01
1993	89.84
1994	89.67
1995	89.5
1996	89.33
1997	89.16
1998	88.99
1999	88.82
2000	88.65
2001	88.5
2002	88.35
2003	88.2
2004	88.05
2005	87.9
2006	87.75
2007	87.6
2008	87.45
2009	87.3
2010	87.15
2011	87
2012	86.85
2013	86.7
2014	86.55
2015	86.4
2016	86.25
2017	86.1
2018	85.95
2019	85.8
2020	85.65
2021	85.5