Year	sq. km
1990	15948.9
1991	16326.48
1992	16704.06
1993	17081.64
1994	17459.22
1995	17836.8
1996	18214.38
1997	18591.96
1998	18969.54
1999	19347.12
2000	19724.7
2001	19825.35
2002	19926
2003	20026.65
2004	20127.3
2005	20227.95
2006	20328.6
2007	20429.25
2008	20529.9
2009	20630.55
2010	20731.2
2011	20792.26
2012	20853.32
2013	20914.38
2014	20975.44
2015	21036.5
2016	21117.4
2017	21198.3
2018	21279.2
2019	21360.1
2020	21441
2021	21521.9