Year	% of land area
1990	31.077287495473144
1991	30.938708462759497
1992	30.800129430045853
1993	30.661550397332203
1994	30.522971364618552
1995	30.38439233190491
1996	30.24581329919126
1997	30.107234266477615
1998	29.968655233763965
1999	29.83007620105032
2000	29.69149716833667
2001	29.54514705709873
2002	29.398796945860784
2003	29.252446834622845
2004	28.924131442223935
2005	28.77864158436841
2006	28.633216145699755
2007	28.487725579335237
2008	28.342335979884936
2009	28.196862667079877
2010	28.050616222883946
2011	27.885613965527867
2012	27.577109245494867
2013	27.413299823052313
2014	27.24950019632985
2015	27.085585965001258
2016	26.91752300107986
2017	26.752923085137464
2018	26.588425465894193
2019	26.419656921654116
2020	26.252612454068924
2021	26.084410406106528