Year	% of land area
1961	31.760507537012312
1962	31.66738606030161
1963	31.507267292708462
1964	31.260698209428334
1965	31.052881009473992
1966	30.758523767330622
1967	30.61893946202817
1968	30.43245454937677
1969	30.38051980200705
1970	30.109330040729805
1971	29.44805574223331
1972	29.31742535632039
1973	29.157252919760204
1974	29.138190826938693
1975	29.069867556236627
1976	28.985554821160818
1977	28.98655067202129
1978	29.050062152507284
1979	29.012467278217905
1980	28.992887672983798
1981	28.96603539137741
1982	28.964780593731653
1983	28.82616595422753
1984	28.904846163067646
1985	28.89082452963471
1986	28.90228665855211
1987	28.956091894780883
1988	28.815566237559903
1989	28.59592396234066
1990	28.559580015359632
1991	28.358875862144004
1992	28.258209414588492
1993	28.505577143022705
1994	28.308837456657354
1995	27.923262129994562
1996	27.98544410243944
1997	27.958216904699427
1998	27.670478996549082
1999	27.634875002419747
2000	27.405663600297544
2001	26.77742442804716
2002	26.42624389752873
2003	26.20518158422054
2004	26.109308475527246
2005	25.994839144694037
2006	25.808931601902746
2007	25.434762428683253
2008	25.606671368556178
2009	25.549699792009545
2010	25.2962997088396
2011	25.241281752296743
2012	25.288146720087397
2013	25.091892910130124
2014	25.05999936319814
2015	24.994196307929617
2016	24.897871776526465
2017	24.897894386024014
2018	24.764432716917632
2019	24.895455358084483
2020	24.73528311488717
2021	24.737844485801332