Year	% of land area
1961	32.50630277322022
1962	32.606346792588745
1963	32.424266677338025
1964	31.852014886550084
1965	31.946056264756496
1966	31.031653927728197
1967	31.49385729721077
1968	31.397815038616994
1969	32.17815838969146
1970	31.393813277842252
1971	32.69238464924567
1972	32.59033974948978
1973	32.12213373884509
1974	31.851925962981493
1975	31.66543241999079
1976	31.340953219769002
1977	31.288785682828202
1978	31.30943086501311
1979	31.18468991472154
1980	31.14901795903658
1981	31.171665398630523
1982	31.16365674928923
1983	31.219590332979596
1984	31.337097549255166
1985	31.162902450744834
1986	31.164904693256446
1987	31.202947300977097
1988	31.188931603395805
1989	31.058785840140956
1990	30.704388915585458
1991	30.550216242191254
1992	30.43608841902931
1993	29.997597308986062
1994	29.645202626942176
1995	28.12149607560468
1996	28.932404292807945
1997	28.6020342783918
1998	27.398686528912382
1999	26.956190933845907
2000	26.853707414829657
2001	26.20556848270882
2002	25.86766591856364
2003	26.07519881412632
2004	26.092792179173845
2005	25.873089022020075
2006	25.492003687522548
2007	25.21688605718178
2008	25.03608660785886
2009	25.061163919303738
2010	25.0554988900222
2011	24.863967352164522
2012	25.12944563283421
2013	24.351772255652627
2014	24.545690809859856
2015	24.573100562181157
2016	24.695894820283286
2017	24.529740774322995
2018	23.78736818203782
2019	23.644962165024644
2020	23.299456060683568
2021	23.112437562789