Year	% of land area
1961	21.675717610550816
1962	22.211016291698993
1963	23.716058960434445
1964	23.281613653995343
1965	23.204034134988362
1966	23.235065942591156
1967	23.429014740108613
1968	23.685027152831655
1969	23.405740884406516
1970	23.351435221101628
1971	23.204034134988362
1972	23.157486423584174
1973	22.940263770364623
1974	22.87044220325834
1975	22.56012412723041
1976	22.404965089216446
1977	22.249806051202484
1978	22.676493405740885
1979	22.723041117145073
1980	22.52133436772692
1981	22.69200930954228
1982	22.715283165244376
1983	22.498060512024825
1984	22.668735453840185
1985	22.420480993017843
1986	22.33514352211016
1987	22.265321955003877
1988	22.211016291698993
1989	22.443754848719937
1990	22.490302560124128
1991	22.242048099301783
1992	22.21877424359969
1993	22.024825446082232
1994	22.00155159038014
1995	21.885182311869666
1996	21.799844840961985
1997	21.636927851047325
1998	21.598138091543834
1999	21.42746314972847
2000	21.26454615981381
2001	21.101629169899148
2002	21.078355314197054
2003	21.039565554693564
2004	20.395655546935608
2005	20.473235065942593
2006	20.046547711404187
2007	19.91466252909232
2008	19.829325058184637
2009	19.759503491078355
2010	19.91466252909232
2011	19.798293250581846
2012	19.705197827773468
2013	19.47245927075252
2014	17.253685027152834
2015	16.842513576415826
2016	16.60201706749418
2017	16.624417377812257
2018	16.61206128782002
2019	16.539413498836307
2020	16.539413498836307
2021	16.539413498836307