Year	% of land area
1961	0.6901828443735105
1962	0.7055538942340194
1963	0.705614626202685
1964	0.7160897751564747
1965	0.7207694976334329
1966	0.7252559559934979
1967	0.7289189556052079
1968	0.7383624421738102
1969	0.7469759079938926
1970	0.7568461376723413
1971	0.7663709022340246
1972	0.7746478455311921
1973	0.787788661792951
1974	0.7982718956630274
1975	0.8081185264849797
1976	0.819958180805672
1977	0.8320187368466898
1978	0.8434152631356324
1979	0.8559991901012345
1980	0.8709308092036878
1981	0.881256358723666
1982	0.8876823950936391
1983	0.8873824498135424
1984	0.896381477867236
1985	0.9187130183487051
1986	0.9436038506460885
1987	0.9731225287112639
1988	0.9943434707663501
1989	1.0042695752099697
1990	1.025546680863395
1991	1.0341078310556384
1992	0.908563439637893
1993	0.928535578616912
1994	0.9511442383887523
1995	0.9600323841046337
1996	0.9701513316640332
1997	0.9819957897362235
1998	0.9928132537014629
1999	1.0150891654360046
2000	1.0287584638128104
2001	1.0468258118841371
2002	1.0575823166417355
2003	1.07402025819221
2004	1.0950896252860136
2005	1.119186481435361
2006	1.1426971351845554
2007	1.1676589212019453
2008	1.1800324659851997
2009	1.1966302253112973
2010	1.2197507273868196
2011	1.2391543889180396
2012	1.2543337035478537
2013	1.2721073618825087
2014	1.2835225425789136
2015	1.3063479260917112
2016	1.3133371720905163
2017	1.3448789819457923
2018	1.3745797765406336
2019	1.3933981487774039
2020	1.4036796501666027
2021	1.4170762632414386