Year	% of land area
1961	28.259029900023027
1962	28.435439795184
1963	28.59263916424032
1964	28.758212738098198
1965	28.939230953146975
1966	29.103094584587293
1967	29.243595688979426
1968	29.42817419469234
1969	29.554785151000452
1970	29.763984821728723
1971	30.059032627907705
1972	30.324941210073597
1973	30.55596509651497
1974	30.813009196782378
1975	31.06493103213807
1976	31.383822739334402
1977	31.71700381432301
1978	32.01708925624161
1979	32.31041014427594
1980	32.60575399937579
1981	32.75800750191354
1982	32.88017934108483
1983	33.129418955224
1984	33.31335581206243
1985	33.442890562443935
1986	33.4336328820137
1987	33.425291207872064
1988	33.41074056248405
1989	33.40506560689259
1990	33.52089583590745
1991	33.52166392907632
1992	33.45421928229066
1993	33.42567814783108
1994	33.365931687676806
1995	33.31639363473638
1996	33.35397273869488
1997	33.3957454807194
1998	33.512045080475524
1999	33.54299557207846
2000	33.52209816371017
2001	33.39102195420705
2002	33.42623886993593
2003	33.433539732982915
2004	33.51191803182865
2005	33.56771582401442
2006	33.55444658212023
2007	33.61265589320924
2008	33.347842020983414
2009	33.21482284095639
2010	33.289602419086584
2011	33.2166867400181
2012	33.22502946725138
2013	33.221362883476004
2014	33.02273973942788
2015	33.046150574296355
2016	32.91537774139359
2017	32.7315668203922
2018	32.68231898485608
2019	32.69768336206459
2020	32.838864426825644
2021	32.83235546794199