Year	% of land area
1961	16.59647512531789
1962	16.687246606845388
1963	16.759508819793254
1964	16.94079823122387
1965	17.220212121288956
1966	17.334817455508027
1967	17.41139004607033
1968	17.395162742110106
1969	17.087097518490253
1970	17.181925826007806
1971	17.149978321336114
1972	17.20246350758246
1973	17.463875232316674
1974	17.356445409067515
1975	17.553886058971038
1976	17.522192105923725
1977	17.624626962172634
1978	17.779547004667887
1979	17.85984680410855
1980	18.180538898622455
1981	17.990324470013718
1982	18.547808426534683
1983	18.065984274728255
1984	18.367659997413774
1985	18.53393915268118
1986	18.192912217892125
1987	18.52788180437478
1988	18.322984201198285
1989	18.604652165204097
1990	18.422802404683605
1991	18.718136801243418
1992	18.251088829739757
1993	18.278573341236836
1994	18.591179048695807
1995	19.072619164776615
1996	19.029361212257143
1997	19.22208693701838
1998	19.368604627211703
1999	19.725427235505347
2000	19.624903109292717
2001	19.887891931310463
2002	19.8828233004504
2003	19.886585079341813
2004	19.74394855682524
2005	19.735975390763866
2006	19.827504326661828
2007	19.767803497479655
2008	19.665321670151876
2009	19.888027507383136
2010	19.693513174616005
2011	19.973124214714943
2012	19.95809597307621
2013	20.013628603765643
2014	20.01522686522249
2015	19.99189658278919
2016	20.13409552290412
2017	20.190466176978386
2018	20.237088946500183
2019	20.19955867511304
2020	20.288638468099858
2021	20.191261597633364