Year	% of land area
1961	30.98141410493268
1962	30.982663053336488
1963	31.007054280987383
1964	31.01800094640902
1965	31.04246564161308
1966	31.050400137354938
1967	31.10322330808082
1968	31.133565407538107
1969	31.190429293688087
1970	31.254493000048267
1971	31.38658766063956
1972	31.49994809517369
1973	31.496808082571306
1974	31.550806892834256
1975	31.529648175343468
1976	31.5997364270317
1977	31.621997161058466
1978	31.66607782249761
1979	31.678493875469634
1980	31.758867614827
1981	31.454314324943976
1982	31.48030281357311
1983	31.528747460494728
1984	31.94226961481069
1985	32.44217664134894
1986	33.02653927649382
1987	33.582998852947725
1988	34.18697738243302
1989	34.69778408718979
1990	35.10945338436992
1991	35.159977169156086
1992	35.321082698799266
1993	36.09618121709613
1994	36.750653887897606
1995	37.38082591756884
1996	37.97764103568537
1997	38.488462616458186
1998	39.096353462027615
1999	39.622189599315455
2000	39.65694078014281
2001	39.679751445678264
2002	39.7529968083444
2003	39.94156576056088
2004	39.99125265653587
2005	40.04847797605085
2006	40.11976585503042
2007	40.17216897451102
2008	40.11155964720891
2009	40.12213098979626
2010	40.16030262132148
2011	40.17641904211003
2012	39.789966964691025
2013	39.83865016813302
2014	39.83442149624595
2015	39.872574517607234
2016	39.937813931025225
2017	39.984452025986734
2018	39.96973753271624
2019	39.90703090650282
2020	39.97329047813187
2021	39.970742355345294