Year	% of land area
1961	0.3783058774976786
1962	0.39550159920211847
1963	0.4126973209065584
1964	0.42989304261099837
1965	0.44708876431543826
1966	0.4642844860198782
1967	0.4814802077243182
1968	0.49867592942875816
1969	0.5158716511331981
1970	0.533067372837638
1971	0.550263094542078
1972	0.5674588162465178
1973	0.5846545379509578
1974	0.6035698318258417
1975	0.7961619149155691
1976	0.816796780960897
1977	0.8357120748357809
1978	0.8597860852219967
1979	0.8597860852219967
1980	0.8597860852219967
1981	0.8855796677786567
1982	0.9113732503353166
1983	0.9199711111875366
1984	0.9285689720397564
1985	0.9371668328919764
1986	0.9457646937441965
1987	0.9629604154486364
1988	0.9801561371530763
1989	1.0059497197097362
1990	1.0403411631186161
1991	1.0317433022663962
1992	1.0145475805619562
1993	1.0145475805619562
1994	0.9973518588575163
1995	0.9973518588575163
1996	0.9973518588575163
1997	1.0145475805619562
1998	1.0145475805619562
1999	1.0317433022663962
2000	1.0317433022663962
2001	1.0317433022663962
2002	1.0317433022663962
2003	1.0317433022663962
2004	1.0317433022663962
2005	1.0317433022663962
2006	1.0317433022663962
2007	1.0317433022663962
2008	1.0317433022663962
2009	1.0317433022663962
2010	1.0317433022663962
2011	1.0312910905043873
2012	1.0312910905043873
2013	1.0312822275696116
2014	1.0312822275696116
2015	1.0312822275696116
2016	1.0312822275696116
2017	1.0312822275696116
2018	1.0312822275696116
2019	1.0312822275696116
2020	1.0312822275696116
2021	1.0312822275696116