Year	sq. km
1961	100
1962	100
1963	100
1964	100
1965	100
1966	100
1967	100
1968	100
1969	100
1970	100
1971	100
1972	100
1973	100
1974	100
1975	100
1976	100
1977	100
1978	100
1979	100
1980	100
1981	100
1982	100
1983	100
1984	100
1985	100
1986	100
1987	100
1988	100
1989	100
1990	100
1991	100
1992	100
1993	100
1994	100
1995	100
1996	100
1997	100
1998	100
1999	100
2000	99
2001	97.9
2002	96.9
2003	95.8
2004	94.8
2005	93.7
2006	92.7
2007	91.6
2008	90.6
2009	89.5
2010	88.5
2011	87.4
2012	86.4
2013	85.3
2014	84.3
2015	83.2
2016	82.2
2017	81.1
2018	81
2019	81
2020	81
2021	81