Year	% of land area
1990	13.894049346879536
1991	13.885812772133526
1992	13.877576197387517
1993	13.869339622641508
1994	13.8611030478955
1995	13.852866473149492
1996	13.844629898403483
1997	13.836393323657475
1998	13.828156748911466
1999	13.819920174165457
2000	13.81168359941945
2001	13.80344702467344
2002	13.795210449927431
2003	13.786973875181422
2004	13.778737300435415
2005	13.770500725689406
2006	13.762264150943397
2007	13.75402757619739
2008	13.74579100145138
2009	13.73755442670537
2010	13.729317851959363
2011	13.616618287373003
2012	13.503918722786649
2013	13.39121915820029
2014	13.278519593613932
2015	13.165820029027575
2016	13.052975326560231
2017	12.940130624092888
2018	12.827285921625545
2019	12.714441219158202
2020	12.601596516690854
2021	12.488751814223512