Year	% of land area
1990	36.113866967305526
1991	37.340698985343856
1992	38.567531003382186
1993	39.79436302142052
1994	41.021195039458846
1995	42.24802705749718
1996	43.47485907553551
1997	44.70169109357384
1998	45.92852311161218
1999	47.15535512965051
2000	48.38218714768884
2001	49.08455467869222
2002	49.786922209695604
2003	50.489289740698986
2004	51.19165727170236
2005	51.89402480270575
2006	52.59639233370913
2007	53.29875986471252
2008	54.0011273957159
2009	54.70349492671927
2010	55.40586245772266
2011	55.46065388951522
2012	55.51544532130778
2013	55.57023675310033
2014	55.62502818489289
2015	55.67981961668546
2016	55.735062006764366
2017	55.7903043968433
2018	55.845546786922206
2019	55.90078917700112
2020	55.956031567080046
2021	56.011273957158956