Year	% of land area
1961	33.44215910327566
1962	33.735988682119924
1963	34.280117531831536
1964	34.87865926651431
1965	34.50865164871041
1966	31.956687343562955
1967	31.973011209054302
1968	30.346065948416584
1969	30.60724779627816
1970	30.74872129720318
1971	30.72695614321471
1972	31.075198607030146
1973	30.199151158994447
1974	30.917401240613778
1975	27.8866035477201
1976	28.621177494830775
1977	27.658069430841227
1978	28.017194471650885
1979	28.45793883991729
1980	28.45793883991729
1981	28.702796822287517
1982	28.773533572750026
1983	27.652628142344106
1984	27.772336489280665
1985	27.413211448470996
1986	27.277179236043096
1987	27.09761671563826
1988	26.183480248122752
1989	26.10730220916313
1990	26.580694308412234
1991	26.13994994014583
1992	25.933180977255414
1993	25.960387419740993
1994	26.183480248122752
1995	26.112743497660247
1996	25.786266187833277
1997	25.960387419740993
1998	25.623027532919796
1999	25.579497224942866
2000	24.7143323539014
2001	25.220372184133204
2002	24.991838067254328
2003	25.19200392178223
2004	25.913820341014326
2005	25.467124257776323
2006	25.431574361487776
2007	25.789588324983665
2008	25.588107166194728
2009	25.430189501197997
2010	25.52415182704351
2011	25.3880084953439
2012	25.40434569514785
2013	25.3880084953439
2014	25.38256276207591
2015	25.40434569514785
2016	25.402167401840657
2017	25.4231334749224
2018	25.389767467189454
2019	25.367058759461962
2020	25.380477046234272
2021	25.380477046234272