Year	% of land area
1961	28.28818443057397
1962	28.475421872163164
1963	28.64352203293426
1964	28.84286164976614
1965	29.013602466312705
1966	29.173227616755348
1967	29.31766152293494
1968	29.506239221889423
1969	29.63273659827335
1970	29.85389899302329
1971	30.1485015125477
1972	30.43726967751913
1973	30.679120000964588
1974	30.923655826492375
1975	31.182831562412314
1976	31.50904795837053
1977	31.842037689413402
1978	32.1359158502145
1979	32.42262438005654
1980	32.719315213446556
1981	32.87024455858323
1982	32.99885818585628
1983	33.25118452816674
1984	33.431999888195186
1985	33.56444158477445
1986	33.56675253150215
1987	33.57211604363218
1988	33.560697872300565
1989	33.55366420350629
1990	33.66636083598912
1991	33.66707418458716
1992	33.60055985115012
1993	33.565026920845575
1994	33.503271670951854
1995	33.45390150474134
1996	33.48780201499779
1997	33.531997636155246
1998	33.646173052156115
1999	33.67544809924174
2000	33.648812152071834
2001	33.52304243164377
2002	33.55889132797524
2003	33.56501127277132
2004	33.6370059320734
2005	33.69750752098721
2006	33.68356118847325
2007	33.74054475239371
2008	33.47485745900506
2009	33.340110637798475
2010	33.411869278426316
2011	33.33612963986293
2012	33.34468031048235
2013	33.341665156281
2014	33.14119769373248
2015	33.16212512273755
2016	33.03131062539599
2017	32.85247017325542
2018	32.803249672180264
2019	32.82356342475496
2020	32.96386390775017
2021	32.957395546878125