Year	sq. km
1961	90
1962	90
1963	90
1964	90
1965	90
1966	90
1967	90
1968	90
1969	90
1970	90
1971	90
1972	90
1973	90
1974	90
1975	90
1976	90
1977	90
1978	90
1979	90
1980	90
1981	90
1982	90
1983	90
1984	90
1985	90
1986	80
1987	80
1988	80
1989	80
1990	70
1991	70
1992	70
1993	70
1994	70
1995	70
1996	70
1997	70
1998	70
1999	70
2000	70
2001	69
2002	67.7
2003	66.4
2004	65.1
2005	63.8
2006	62.5
2007	61.2
2008	59.9
2009	58.6
2010	57.3
2011	56
2012	54.7
2013	53.4
2014	52.4
2015	52.2
2016	52
2017	51.8
2018	51.8
2019	51.7
2020	51.7
2021	51.7