Year	% of land area
1961	38.43442104311669
1962	37.548585374672335
1963	37.40395914308958
1964	37.783603000994304
1965	37.666094187833316
1966	37.657055048359396
1967	37.476272258880954
1968	37.548585374672335
1969	37.58474193256802
1970	37.44011570098527
1971	37.349724306246046
1972	37.31356774835036
1973	37.24125463255898
1974	37.042393564132695
1975	35.767874898309685
1976	35.614209527253
1977	35.58709210883124
1978	35.487661574618095
1979	35.22552652987436
1980	34.59278676669981
1981	34.56566934827804
1982	34.511434511434516
1983	34.457199674590974
1984	34.41200397722137
1985	34.439121395643134
1986	34.520473650908436
1987	34.57470848775196
1988	34.7102955798608
1989	34.78260869565217
1990	34.85492181144355
1991	34.92723492723493
1992	36.58139745096267
1993	36.726023682545424
1994	36.16559703516225
1995	36.13847961674049
1996	37.991503208894514
1997	38.85022145891711
1998	31.962397179788482
1999	32.342041037693214
2000	31.87200578504926
2001	31.338696556087857
2002	30.83639705882353
2003	30.550703318929852
2004	30.461566752482533
2005	29.20655375552283
2006	28.83181441590721
2007	28.404382653530984
2008	28.432004419482553
2009	28.979366249078854
2010	29.347826086956523
2011	29.937361827560792
2012	30.554532056005897
2013	32.046794399410466
2014	32.11127487103906
2015	32.32958732498158
2016	32.20338983050847
2017	32.13964627855564
2018	32.03758290346352
2019	32.01915991156964
2020	32.16654384672071
2021	32.244615880619016