Year	sq. km
1961	18110
1962	18160
1963	17720
1964	17610
1965	17580
1966	17550
1967	17580
1968	17520
1969	17630
1970	17630
1971	17560
1972	17480
1973	17630
1974	18010
1975	17910
1976	17810
1977	17680
1978	17760
1979	16890
1980	14710
1981	14600
1982	15310
1983	15280
1984	15240
1985	15160
1986	15100
1987	15010
1988	14960
1989	14660
1990	14430
1991	14230
1992	14710
1993	14830
1994	14920
1995	14950
1996	15010
1997	15100
1998	15180
1999	15210
2000	13896
2001	13868
2002	13891
2003	13922
2004	13913
2005	13830
2006	13800
2007	13669
2008	13653
2009	13636
2010	13557
2011	13357
2012	13320
2013	13365
2014	13313
2015	13280
2016	13508
2017	13270
2018	13540
2019	13564.226
2020	13646.093
2021	13656.7