Year	% of land area
1961	13.500931098696462
1962	14.013035381750466
1963	14.823091247672254
1964	16.405959031657353
1965	15.083798882681565
1966	14.441340782122905
1967	15.763500931098696
1968	18.12849162011173
1969	18.091247672253257
1970	21.508379888268156
1971	21.201117318435756
1972	24.30167597765363
1973	25.921787709497206
1974	24.543761638733706
1975	26.722532588454378
1976	28.18435754189944
1977	28.221601489757912
1978	28.268156424581004
1979	27.737430167597765
1980	27.746741154562383
1981	27.932960893854748
1982	28.398510242085663
1983	28.86405959031657
1984	28.9292364990689
1985	29.497206703910617
1986	30.26070763500931
1987	31.00558659217877
1988	31.471135940409685
1989	31.666666666666664
1990	31.573556797020487
1991	31.98324022346369
1992	33.28677839851024
1993	33.798882681564244
1994	34.320297951582866
1995	34.30167597765363
1996	32.4487895716946
1997	33.78026070763501
1998	33.27746741154562
1999	33.61266294227188
2000	32.625698324022345
2001	34.81378026070763
2002	35.69884387630417
2003	35.26315789473684
2004	34.82755380133446
2005	34.49830890642615
2006	34.14450812740768
2007	33.568207440811726
2008	32.96317173994739
2009	32.3750469748215
2010	31.79255918827508
2011	31.079045132552896
2012	29.39455597333308
2013	30.28593360199578
2014	29.68631032493751
2015	28.950048030739673
2016	28.73125720876586
2017	28.021194605009637
2018	28.021194605009637
2019	28.021194605009637
2020	28.021194605009637
2021	28.021194605009637