Year	% of land area
1990	18.5363851044505
1991	18.467211625794732
1992	18.398038147138966
1993	19.0395
1994	18.9665
1995	18.8935
1996	18.820500000000003
1997	18.7475
1998	18.6745
1999	18.6015
2000	18.5285
2001	18.4555
2002	18.3825
2003	18.3095
2004	16.158553674083446
2005	16.093836404357365
2006	16.028963389221186
2007	15.964029924857842
2008	15.900232598751597
2009	15.835264101689225
2010	15.77082944449203
2011	15.70608868876999
2012	15.641308877769806
2013	15.576763602424434
2014	15.512544216909424
2015	15.447844112530476
2016	15.382897618115429
2017	15.31829055196548
2018	15.253489582089907
2019	15.188678565010402
2020	15.123989533793422
2021	15.059305980114601