Year	% of land area
1961	13.246875
1962	13.35859375
1963	13.6171875
1964	13.803125
1965	13.8671875
1966	13.80859375
1967	13.815625
1968	13.890625
1969	13.921093749999999
1970	13.99453125
1971	14.0015625
1972	14.503906250000002
1973	14.543142734375
1974	14.584723046875
1975	14.62630328125
1976	14.667883515624998
1977	14.725088750000001
1978	14.7744815625
1979	14.823874296875001
1980	14.86545453125
1981	14.907034765625
1982	14.956427578125
1983	14.9980078125
1984	15.047400546875
1985	15.096793359374999
1986	15.153998593749998
1987	15.203391328124999
1988	15.252784062500002
1989	15.302176874999999
1990	17.528913359375
1991	17.57830609375
1992	17.627698828125
1993	17.677091640625
1994	17.46078125
1995	17.575625
1996	17.690390625
1997	17.80515625
1998	17.919921875
1999	18.0346875
2000	18.149453125
2001	18.26421875
2002	18.378984374999998
2003	18.493750000000002
2004	18.608515625
2005	18.744374999999998
2006	18.869296875
2007	18.994218749999998
2008	19.119921875000003
2009	19.24484375
2010	19.370546875
2011	19.50328125
2012	19.609578125
2013	19.5057578125
2014	19.399671875
2015	19.293596875
2016	19.09609375
2017	19.154771875
2018	19.295772656249998
2019	19.1236640625
2020	19.5288984375
2021	19.934132031249998