Year	% of land area
1990	21.504848327890247
1991	21.627712995133173
1992	21.7505776623761
1993	21.873442329619028
1994	21.996306996861957
1995	22.119171664104883
1996	22.242036331347812
1997	22.364900998590738
1998	22.487765665833667
1999	22.610630333076596
2000	22.73349500031952
2001	22.797567595747328
2002	22.861640191175134
2003	22.925712786602944
2004	22.989785382030746
2005	23.053857977458556
2006	23.11793057288636
2007	23.182003168314168
2008	23.246075763741974
2009	23.31014835916978
2010	23.37422095459759
2011	23.463821686471434
2012	23.553422418345278
2013	23.643023150219125
2014	23.73262388209297
2015	23.822224613966817
2016	23.91182534584066
2017	24.00142607771451
2018	24.091026809588353
2019	24.1806275414622
2020	24.27022827333605
2021	24.359829005209892