Year	% of land area
1961	4.08338993864319
1962	4.119639644462885
1963	4.15588935028258
1964	4.192139056102275
1965	4.228388761921971
1966	4.264080779959825
1967	4.271665333792868
1968	4.2792498876259115
1969	4.286834441458956
1970	4.294418995292
1971	4.301780474012308
1972	4.315388055889239
1973	4.3289956377661705
1974	4.342603219643102
1975	4.356210801520033
1976	4.369595308284229
1977	4.4008258240673515
1978	4.432056339850473
1979	4.463286855633595
1980	4.494517371416717
1981	4.525970962312575
1982	4.548278473586233
1983	4.570585984859892
1984	4.592893496133551
1985	4.615201007407209
1986	4.637620056237235
1987	4.631708565749716
1988	4.625797075262197
1989	4.619885584774678
1990	4.613974094287157
1991	4.608442935713099
1992	4.602708801093961
1993	4.596908848162809
1994	4.591108895231658
1995	4.5853089423005065
1996	4.579620526925724
1997	4.577166700685622
1998	4.5747128744455186
1999	4.572259048205416
2000	4.569805221965314
2001	4.567239858168843
2002	4.530097851898201
2003	4.49295584562756
2004	4.455813839356919
2005	4.418671833086277
2006	4.381529826815636
2007	4.3370263418246875
2008	4.292522856833739
2009	4.24801937184279
2010	4.203515886851841
2011	4.158677789191787
2012	4.186450640727492
2013	4.214223492263197
2014	4.241996343798903
2015	4.269880732890975
2016	4.297542046870312
2017	4.295199758186578
2018	4.315388055889239
2019	4.310703478521771
2020	4.2646384677416656
2021	4.353203545461786