Year	% of land area
1961	0.5654844980826451
1962	0.571159225540117
1963	0.5749071939408676
1964	0.5791200588909231
1965	0.581895573419276
1966	0.5865728044820071
1967	0.5900236990611407
1968	0.591584287381973
1969	0.5939522120650605
1970	0.6025025369763068
1971	0.6058006513218291
1972	0.608294993907881
1973	0.615404935395116
1974	0.6194352878082963
1975	0.6221143338819872
1976	0.624745287086154
1977	0.6243224774085127
1978	0.6301975947115753
1979	0.6314275422136129
1980	0.6348007036418744
1981	0.638913564931155
1982	0.6365728341850001
1983	0.6417625929085216
1984	0.638907591341874
1985	0.6388387812682098
1986	0.6380721076759422
1987	0.640018682581329
1988	0.6407036046469133
1989	0.6410426537606033
1990	0.643335150424798
1991	0.6448877823957757
1992	0.6435141643541807
1993	0.6467215109441191
1994	0.6503305037175738
1995	0.6357153516876145
1996	0.6257643137272568
1997	0.637359792433159
1998	0.6439560498170503
1999	0.6527006428956875
2000	0.6551786026253775
2001	0.6580088168473818
2002	0.6479879839124094
2003	0.6364194683287302
2004	0.6496455414199491
2005	0.6542980063656046
2006	0.6513426880876607
2007	0.6549876065744177
2008	0.6577238699672199
2009	0.653730621835208
2010	0.6567899086049831
2011	0.6614212960468181
2012	0.6754164689082189
2013	0.6722840361283154
2014	0.6773962264735758
2015	0.6826654295478053
2016	0.6766910281355842
2017	0.6787066449569252
2018	0.6934251039005469
2019	0.7031577263182258
2020	0.7028173012291121
2021	0.7100522943857663