Year	sq. km
1991	636.08
1992	636.36
1993	636.64
1994	636.92
1995	637.2
1996	637.48
1997	637.76
1998	638.04
1999	638.32
2000	638.6
2001	638.87
2002	639.14
2003	639.41
2004	639.68
2005	639.95
2006	640.22
2007	640.49
2008	640.76
2009	641.03
2010	641.3
2011	641.58
2012	641.86
2013	642.14
2014	642.42
2015	642.7
2016	643
2017	643.3
2018	643.6
2019	643.9
2020	644.2
2021	644.5