Year	% of land area
1961	15.959237384092786
1962	16.020442513082596
1963	16.07705725739817
1964	16.24996174679438
1965	16.19334700247881
1966	16.433577133763812
1967	16.47489059583193
1968	16.476420724056677
1969	16.47489059583193
1970	16.526914955473266
1971	16.53303546837225
1972	16.53303546837225
1973	15.793983535820303
1974	15.810814946292497
1975	15.832236741438932
1976	15.855188664810111
1977	15.84600789546164
1978	15.862839305933838
1979	15.878140588181289
1980	15.890381613979251
1981	15.94546623007008
1982	15.976068794564984
1983	15.97147840989075
1984	15.946996358294824
1985	15.957707255868042
1986	15.966888025216514
1987	15.946996358294824
1988	15.87202007528231
1989	15.905682896226702
1990	15.956177127643297
1991	15.937815588946352
1992	15.910273280900938
1993	15.983719435688712
1994	15.94546623007008
1995	15.989839948587692
1996	16.072466872723933
1997	16.095418796095114
1998	16.086238026746642
1999	16.233130336322183
2000	16.543746365945466
2001	16.73807265048811
2002	16.716650855341676
2003	16.803868164152156
2004	16.95999510269046
2005	17.23858209868985
2006	17.74679786371218
2007	18.337617823479004
2008	18.791997673386295
2009	19.043318536660035
2010	19.17460123075039
2011	19.22270354666381
2012	19.213044476766438
2013	19.273289642922766
2014	19.342193911925033
2015	19.521344858210327
2016	19.54716749900426
2017	19.997855227882038
2018	20.026505285736174
2019	19.885705530871764
2020	19.887538878759557
2021	19.887538878759557