Year	% of land area
1961	35.90515715468856
1962	35.89351511228688
1963	35.84355988447741
1964	35.81089697031524
1965	35.792018234356675
1966	35.79039766205436
1967	35.78108092358837
1968	35.789739498590585
1969	35.72550336543505
1970	35.74448455136675
1971	35.763279464620034
1972	35.904405854885574
1973	35.97050787572484
1974	35.99477185785017
1975	36.00550872561098
1976	36.025620209208626
1977	36.08485913482642
1978	36.1598692580395
1979	36.25873486209813
1980	36.25192414937146
1981	36.14415605994333
1982	36.22085320423638
1983	36.24825791168336
1984	36.54672288393801
1985	36.83937673294925
1986	37.069723805093744
1987	37.45733576466373
1988	37.672638110725146
1989	37.93766629102455
1990	38.224326151655
1991	38.25170465056651
1992	39.1230588222272
1993	38.79200808444358
1994	39.06085534409758
1995	39.351144407854136
1996	39.605067080160936
1997	39.88713296926766
1998	40.221357695189674
1999	40.522974869096345
2000	40.47256120707645
2001	40.580735091168116
2002	40.64060821935309
2003	40.66363933387302
2004	40.62862868120224
2005	40.165698713714214
2006	40.20365120192654
2007	40.257620421576675
2008	40.00754445021855
2009	39.95684057174155
2010	39.99603510540065
2011	39.99087607933308
2012	39.977284741441764
2013	39.92693042415752
2014	39.846864511987114
2015	39.87377816464844
2016	39.86648946571542
2017	39.918964875141455
2018	39.90574034701863
2019	39.90863595314384
2020	40.02369487178849
2021	40.05406173512433