Year	% of land area
1961	19.953656024716786
1962	19.953656024716786
1963	19.953656024716786
1964	20.468589083419158
1965	20.468589083419158
1966	20.468589083419158
1967	20.468589083419158
1968	20.468589083419158
1969	20.507209062821833
1970	20.55226570545829
1971	20.59732234809475
1972	20.790422245108136
1973	21.176622039134912
1974	21.498455200823894
1975	21.949021627188465
1976	22.39958805355304
1977	22.70211122554068
1978	21.968331616889806
1979	21.92327497425335
1980	20.53939237899073
1981	20.40422245108136
1982	20.339855818743562
1983	20.21112255406797
1984	20.08238928939238
1985	19.7605561277034
1986	19.503089598352215
1987	19.181256436663233
1988	18.89804325437693
1989	18.730690010298662
1990	18.72425334706488
1991	18.717816683831103
1992	18.717816683831103
1993	19.226313079299693
1994	18.215756951596294
1995	18.292996910401648
1996	18.312306900102985
1997	18.312306900102985
1998	18.531153450051495
1999	18.72425334706488
2000	18.4346035015448
2001	17.855303810504637
2002	17.835993820803296
2003	17.958290422245106
2004	17.964727085478888
2005	17.57209062821833
2006	17.784500514933058
2007	17.59140061791967
2008	18.247940267765188
2009	17.4240473738414
2010	18.170700308959837
2011	18.273686920700307
2012	18.331616889804327
2013	18.363800205973224
2014	16.658084449021626
2015	16.542224510813593
2016	16.501029866117406
2017	16.779737384140063
2018	16.53964984552008
2019	16.53964984552008
2020	18.224124613800203
2021	18.224124613800203