Year	% of land area
1961	26.633300563052998
1962	26.722674054875323
1963	26.767360800786488
1964	26.81204754669765
1965	26.856734292608813
1966	26.94610778443114
1967	27.035481276253464
1968	27.080168022164624
1969	27.080168022164624
1970	27.16954151398695
1971	27.214228259898114
1972	27.52703548127625
1973	27.616408973098576
1974	27.670033068191973
1975	28.018589686299045
1976	28.33139690767718
1977	29.001698096344626
1978	29.108946286531417
1979	29.108946286531417
1980	29.108946286531417
1981	29.171507730807043
1982	29.216194476718204
1983	29.225131825900437
1984	29.287693270176067
1985	29.2966306193583
1986	29.359192063633927
1987	29.359192063633927
1988	29.359192063633927
1989	30.127804093305926
1990	29.671999285012063
1991	29.86862096702118
1992	29.984806506390203
1993	31.709714898561085
1994	31.45946912145858
1995	31.101975154169274
1996	31.101975154169274
1997	30.342300473679508
1998	30.342300473679508
1999	29.823934221110022
2000	26.231119849852536
2001	26.240057199034766
2002	27.062293323800162
2003	28.17946197157923
2004	28.063276432210206
2005	28.15264992403253
2006	28.242023415854856
2007	28.242023415854856
2008	28.45651979622844
2009	28.581642684779695
2010	29.207257127535975
2011	29.591563142371974
2012	30.011618553936902
2013	30.11886674412369
2014	30.163553490034857
2015	30.163553490034857
2016	30.60148359996425
2017	31.173473947627134
2018	31.361158280454017
2019	31.361158280454017
2020	31.62034140673876
2021	31.959960675663595