Year	% of land area
1961	19.78798586572438
1962	20.141342756183743
1963	20.141342756183743
1964	20.141342756183743
1965	21.908127208480565
1966	21.908127208480565
1967	21.908127208480565
1968	22.261484098939928
1969	22.261484098939928
1970	22.43816254416961
1971	22.614840989399294
1972	22.614840989399294
1973	22.614840989399294
1974	22.614840989399294
1975	22.968197879858657
1976	24.381625441696116
1977	25.08833922261484
1978	25.08833922261484
1979	25.97173144876325
1980	26.148409893992934
1981	27.208480565371023
1982	27.208480565371023
1983	27.420494699646643
1984	27.56183745583039
1985	27.56183745583039
1986	27.703180212014132
1987	27.102473498233216
1988	27.208480565371023
1989	19.151943462897528
1990	19.081272084805654
1991	19.081272084805654
1992	18.374558303886925
1993	18.374558303886925
1994	18.021201413427562
1995	18.021201413427562
1996	18.021201413427562
1997	18.021201413427562
1998	18.021201413427562
1999	17.95053003533569
2000	16.96113074204947
2001	16.96113074204947
2002	16.607773851590103
2003	15.901060070671377
2004	15.19434628975265
2005	14.840989399293287
2006	14.20494699646643
2007	13.604240282685511
2008	13.074204946996467
2009	12.332155477031801
2010	14.664310954063604
2011	16.96113074204947
2012	19.257950530035338
2013	21.554770318021202
2014	23.851590106007066
2015	26.7208480565371
2016	24.314487632508833
2017	22.302158273381295
2018	19.845323741007196
2019	17.77338129496403
2020	17.77338129496403
2021	17.77338129496403