Year	% of land area
1961	3.5402481878933525
1962	3.5600179441817112
1963	3.5964481923835243
1964	3.616476367018192
1965	3.617877276295307
1966	3.6484861105366115
1967	3.6774260865869164
1968	3.6679784617951503
1969	3.68522513740802
1970	3.7450425753453023
1971	3.742827603190842
1972	3.7514509889729983
1973	3.7825508125357437
1974	3.805726626875807
1975	3.8274686716708315
1976	3.8311147048511622
1977	3.8138880495958176
1978	3.812218891107355
1979	3.76663713985175
1980	3.7302208200699196
1981	3.7180562437624944
1982	3.7051300694563047
1983	3.7399472746167084
1984	3.7126725825904114
1985	3.6833495634667677
1986	3.6589229877641496
1987	3.628876630407854
1988	3.608299350020366
1989	3.604673920632779
1990	3.603727753559766
1991	3.5469326383336703
1992	3.3330790483688837
1993	3.216579295914165
1994	3.197971719757099
1995	3.1497659153190423
1996	3.1346275660922363
1997	3.152718773543208
1998	3.2011577743976884
1999	3.226799140788887
2000	3.193661821050857
2001	3.1965957172122565
2002	3.1177888385568453
2003	3.098503460489288
2004	3.07580934053064
2005	3.0977309096552
2006	3.0562538995458755
2007	3.02870065639893
2008	3.022240058940642
2009	3.001479001845312
2010	2.994221414678686
2011	2.9402870477069096
2012	3.0212688946411155
2013	2.970244392591144
2014	2.974692459423444
2015	2.9941256523289588
2016	2.9454263833284964
2017	2.9581168821704438
2018	2.9918208246639715
2019	3.011153160178621
2020	2.976766725380446
2021	2.9825208575852353