Year	% of land area
1961	11.905730897009967
1962	11.88496677740864
1963	11.88496677740864
1964	11.853820598006644
1965	11.853820598006644
1966	11.82267441860465
1967	11.82267441860465
1968	11.801910299003323
1969	11.801910299003323
1970	11.781146179401993
1971	11.781146179401993
1972	11.781146179401993
1973	11.781146179401993
1974	11.781146179401993
1975	11.781146179401993
1976	11.781146179401993
1977	11.833056478405316
1978	11.833056478405316
1979	11.833056478405316
1980	11.833056478405316
1981	11.833056478405316
1982	11.874584717607974
1983	11.926495016611295
1984	11.93687707641196
1985	11.957641196013288
1986	12.05107973421927
1987	12.113372093023255
1988	12.082225913621263
1989	12.082225913621263
1990	11.044019933554818
1991	11.358181063122924
1992	11.66860672757475
1993	11.980776578073089
1994	12.293066860465116
1995	12.609138289036546
1996	12.927967192691032
1997	13.242068106312294
1998	13.566669435215948
1999	13.878114617940199
2000	14.193482142857142
2001	14.506779485049833
2002	14.821140988372095
2003	15.135464078073088
2004	15.449584717607973
2005	15.759581602990034
2006	16.069356312292356
2007	16.37438642026578
2008	16.68627284053156
2009	16.996792981727577
2010	17.307252906976743
2011	17.61481623754153
2012	17.926040282392027
2013	18.236620639534884
2014	18.5462344269103
2015	18.858525747508306
2016	19.170293812292357
2017	19.48389015780731
2018	19.797589285714288
2019	19.96511627906977
2020	19.96511627906977
2021	19.96511627906977