Year	% of land area
1961	29.65733889968173
1962	29.909477948166824
1963	30.070681602116316
1964	30.397222337039643
1965	30.33522093167445
1966	30.273219526309266
1967	30.21121812094407
1968	30.078948456165005
1969	29.607737775389577
1970	29.355598726904475
1971	29.479601537634853
1972	29.467201256561815
1973	29.243996197247135
1974	29.21092878105237
1975	28.39251023023189
1976	28.495845905840532
1977	28.607448435497872
1978	28.66944984086306
1979	28.22717314925805
1980	28.595048154424834
1981	28.54958045715703
1982	28.574381019303104
1983	28.51651304096226
1984	28.61158186252222
1985	28.89265490017774
1986	28.685983548960444
1987	28.665316413838717
1988	28.462778489645768
1989	27.702227917166123
1990	27.363286901169758
1991	27.144215268879428
1992	27.090480717562933
1993	25.176704005290784
1994	24.432687140908527
1995	24.536022816517175
1996	25.205637994461206
1997	26.321663291034596
1998	25.846319183234822
1999	24.457487703054603
2000	24.288017195056423
2001	23.357996114578597
2002	23.916008762865292
2003	23.391063530773366
2004	24.052411854668705
2005	23.680403422477575
2006	25.189104286363822
2007	25.151903443144715
2008	24.82122928119704
2009	25.003100070268257
2010	24.676559335344937
2011	25.056834621584755
2012	25.67684867523664
2013	25.89757367833671
2014	25.765717356260076
2015	24.846029843343114
2016	24.90807464969206
2017	25.143138097796886
2018	24.95675360641508
2019	25.154376885876083
2020	24.711702558591327
2021	24.841087091307404