Year	% of land area
1961	35.805729355000125
1962	35.66693330119109
1963	35.529963511247956
1964	34.84146203380049
1965	34.32645562361432
1966	33.71830975626683
1967	33.01154564016027
1968	32.1038924988038
1969	32.07832480468108
1970	31.808037752526637
1971	31.148756496933704
1972	31.09579484482236
1973	31.22180705157004
1974	31.55418707516537
1975	31.654631587790334
1976	31.28572628687683
1977	31.53044564490856
1978	31.6911568651085
1979	31.778817530672104
1980	31.9084822651516
1981	32.00710051391065
1982	32.2353834971492
1983	32.268256246735554
1984	32.523933187962726
1985	32.73212726867629
1986	32.86909705861942
1987	33.17773565195793
1988	32.531238243426365
1989	32.34295043885121
1990	32.47973760240775
1991	32.56465887217249
1992	32.59314858848066
1993	32.93447730501894
1994	33.04843617025162
1995	33.18887586153998
1996	33.247133678862454
1997	33.36602345653309
1998	33.45350149571011
1999	33.517603357403495
2000	33.519916284217274
2001	33.50439306970654
2002	33.55114533929181
2003	33.50229161457069
2004	33.54475342743445
2005	33.56289847449672
2006	33.49240353059134
2007	33.395975213539415
2008	33.36401507057713
2009	33.34118639703264
2010	33.42245647485102
2011	33.374424945713415
2012	33.3877568910634
2013	33.43158794426881
2014	33.48162839667834
2015	33.74753678612455
2016	33.52329711792562
2017	33.7213605158915
2018	33.10413345094666
2019	32.99204101125545
2020	32.793955697762975
2021	32.793955697762975