Year	sq. km
1961	1350
1962	1350
1963	1350
1964	1350
1965	1350
1966	1350
1967	1350
1968	1350
1969	1350
1970	1350
1971	1350
1972	1350
1973	1350
1974	1350
1975	1350
1976	1350
1977	1350
1978	1350
1979	1350
1980	1350
1981	1360
1982	1360
1983	1360
1984	1370
1985	1370
1986	1380
1987	1380
1988	1410
1989	1410
1990	1410
1991	1410
1992	1410
1993	1420
1994	1420
1995	1420
1996	1430
1997	1430
1998	1430
1999	1440
2000	1480
2001	1510
2002	1510
2003	1510
2004	1500
2005	1500
2006	1500
2007	1510
2008	1510
2009	1515
2010	1520
2011	1525
2012	1520
2013	1536
2014	1521
2015	1494
2016	1500
2017	1514
2018	1500
2019	1500
2020	1500
2021	1500