Year	% of land area
1990	30.914475093910294
1991	30.768790031027486
1992	29.85543668102382
1993	29.714200735196854
1994	29.581218716476453
1995	29.439943355190618
1996	29.29866799793633
1997	29.157392632618954
1998	29.016117267301585
1999	28.874841906015757
2000	28.72092809977842
2001	28.59208555286886
2002	28.463180506891486
2003	28.334531228415294
2004	28.03982366416802
2005	27.911696260306027
2006	27.783366101208692
2007	27.654952032746262
2008	27.527097530349607
2009	27.39894925060729
2010	27.270162563271633
2011	27.114440228903078
2012	26.825948852472003
2013	26.67137121718238
2014	26.51795706023507
2015	26.35898743183965
2016	26.204514174429004
2017	26.054552538505547
2018	25.904312426540614
2019	25.750003357862028
2020	25.597241790955167
2021	25.44343716812332