Year	% of land area
1990	20.50490093230688
1991	20.581697895988338
1992	20.65849485966979
1993	20.735291823351247
1994	20.812088787032703
1995	20.888885750714156
1996	20.965682714395616
1997	21.04247967807707
1998	21.119276641758525
1999	21.19607360543998
2000	21.272870569121437
2001	21.395017295825866
2002	21.517164022530302
2003	21.639310749234735
2004	21.761457475939167
2005	21.8836042026436
2006	22.00575092934803
2007	22.127897656052465
2008	22.250044382756897
2009	22.372191109461326
2010	22.494337836165762
2011	22.72857657773976
2012	22.962815319313762
2013	23.197054060887762
2014	23.431292802461765
2015	23.665531544035762
2016	23.830864038131512
2017	23.99619653222726
2018	24.161529026323013
2019	24.326861520418756
2020	24.492153666553694
2021	24.65747271132917