Year	% of land area
1990	29.61093928048185
1991	29.469721634380598
1992	29.32850398827934
1993	29.187286342178087
1994	29.046068696076837
1995	28.904851049975584
1996	28.763633403874326
1997	28.622415757773073
1998	28.481198111671823
1999	28.33998046557057
2000	28.198762819469316
2001	28.052254598730265
2002	27.905746377991207
2003	27.75923815725216
2004	27.6127299365131
2005	27.466221715774054
2006	27.319713495034996
2007	27.17320527429595
2008	27.02669705355689
2009	26.880188832817844
2010	26.733680612078786
2011	26.587172391339735
2012	26.440664170600687
2013	26.29415594986163
2014	26.147647729122582
2015	26.001139508383524
2016	25.838352596451248
2017	25.675565684518965
2018	25.512778772586685
2019	25.349991860654402
2020	25.187204948722126
2021	25.024418036789843