Year	sq. km
1961	21200
1962	21200
1963	21200
1964	21200
1965	21200
1966	21200
1967	21200
1968	21200
1969	21200
1970	20010
1971	19910
1972	19810
1973	19710
1974	19600
1975	19500
1976	19400
1977	19310
1978	19210
1979	19110
1980	19000
1981	19000
1982	19000
1983	19000
1984	19000
1985	19000
1986	19000
1987	19000
1988	19000
1989	19000
1990	19010
1991	19010
1992	19010
1993	19000
1994	19000
1995	18990
1996	18970
1997	18950
1998	18910
1999	18890
2000	18890
2001	18890
2002	18870
2003	18850
2004	18840
2005	18820
2006	18810
2007	18760
2008	18760
2009	18750
2010	18740
2011	18732
2012	18722
2013	18722
2014	18722
2015	18720
2016	18720
2017	18720
2018	18720
2019	18720
2020	18720
2021	18720