Year	% of land area
1961	19.091504530301375
1962	18.851763836522878
1963	18.688018003644395
1964	18.54274605960348
1965	18.544005642933318
1966	18.544005642933318
1967	18.579273976168682
1968	18.55912064289133
1969	18.55912064289133
1970	18.564578837320614
1971	19.075549808123473
1972	19.060014947055514
1973	18.60152661499576
1974	18.614962170513994
1975	18.370183143416156
1976	18.482705920881372
1977	18.4033521711018
1978	18.40797064331119
1979	18.398313837782464
1980	18.40251244888191
1981	16.446379537648944
1982	16.419508426612474
1983	16.49298412085282
1984	16.630698564914724
1985	16.395996204455564
1986	16.243586621545592
1987	16.28179398255057
1988	16.297748704728477
1989	16.27381662146162
1990	16.238548288226255
1991	16.21587578828923
1992	16.317902038005826
1993	16.316642454675993
1994	16.643294398213072
1995	16.647073148202573
1996	16.641614953773292
1997	16.664287453710315
1998	16.72138856466281
1999	16.68150175921805
2000	16.80326148110205
2001	16.840209258777197
2002	16.73356453685121
2003	16.75485149512541
2004	17.27518536868004
2005	17.3028962019364
2006	17.290300368638054
2007	17.320110507444138
2008	17.34404259071099
2009	17.373852729517075
2010	17.37133356285741
2011	17.377211618396636
2012	17.381490003106972
2013	17.395532257929077
2014	17.395265646124262
2015	17.40592281024679
2016	17.36553218842855
2017	17.355010809319733
2018	17.356567989550502
2019	17.347004145287
2020	17.347004145287
2021	17.347004145287