Year	% of land area
1990	20.18359853121175
1991	20.302959830866808
1992	20.422321130521865
1993	20.54396839528155
1994	20.663342977965726
1995	20.7827175606499
1996	20.902092143334077
1997	21.035512249443205
1998	21.15496659242762
1999	21.274420935412028
2000	21.436844454362866
2001	21.576567730417313
2002	21.71629100647177
2003	21.856014282526225
2004	21.995737558580675
2005	22.137931034482758
2006	22.27766990291262
2007	22.417408771342487
2008	22.557147639772346
2009	22.4662321882249
2010	22.604550977576494
2011	22.63642991273611
2012	22.668308847895723
2013	22.70018778305534
2014	22.550230111768574
2015	22.581854043392504
2016	22.55895244356783
2017	22.542954196800352
2018	22.528161297392067
2019	22.512272627657243
2020	22.496274380889762
2021	22.480349550734164