Year	% of land area
1961	0.4032469803576884
1962	0.46786989387654876
1963	0.4711010395524917
1964	0.5492947649103127
1965	0.560280660208519
1966	0.5719127846419138
1967	0.529261661719466
1968	0.5021200380415447
1969	0.482086934850698
1970	0.4807944765803208
1971	0.5008275797711675
1972	0.5014738089063561
1973	0.509874787663808
1974	0.5176295372860712
1975	0.5344314948009748
1976	0.613917678429173
1977	0.7108520487074635
1978	0.7457484220076481
1979	0.7496257968187797
1980	0.7638428377929289
1981	0.783229711848587
1982	0.8084326481209426
1983	0.8478526253674474
1984	0.8620696663415967
1985	0.8743480199101801
1986	0.8439752505563157
1987	0.8620696663415967
1988	0.8821027695324434
1989	0.8879188317491408
1990	0.8853339152083864
1991	0.8840414569380092
1992	0.8801640821268777
1993	0.8737017907749914
1994	0.8536686875841448
1995	0.8536686875841448
1996	0.8536686875841448
1997	0.7929231488764161
1998	0.8698244159638598
1999	0.7690126708744378
2000	0.7586730047114201
2001	0.7602885775493917
2002	0.7619040391129661
2003	0.758609748850015
2004	0.7558329445378373
2005	0.7548679343270122
2006	0.7546265614823437
2007	0.7544339400508414
2008	0.7685565538458841
2009	0.7807919249382054
2010	0.7937045000112495
2011	0.829538214730516
2012	0.8470712163104275
2013	0.8263140004901951
2014	0.8429587655915529
2015	0.8528530387500984
2016	0.8497963789369425
2017	0.849385399466266
2018	0.8523973273484432
2019	0.8532947013275899
2020	0.8606574927429063
2021	0.8557264911168939