Year	% of land area
1961	10.401637748542555
1962	10.242065774585683
1963	9.77316966649703
1964	9.679881435568397
1965	9.449115811692305
1966	9.321458232526808
1967	9.291998791180923
1968	9.134881770669542
1969	9.19380065336131
1970	9.213440280925232
1971	9.225715048152685
1972	9.166796165460916
1973	9.127516910333071
1974	9.169251118906406
1975	9.147156537896993
1976	9.169251118906406
1977	9.137336724115032
1978	9.152066444787975
1979	9.110332236214639
1980	9.093147562096206
1981	9.021953912176986
1982	8.985129610494631
1983	8.926210727802864
1984	8.864836891665604
1985	8.577607338543237
1986	8.53341817652441
1987	8.481864154169113
1988	8.437674992150287
1989	8.39103087668597
1990	8.378756109458518
1991	8.24373366995655
1992	8.209364321719685
1993	8.23882376306557
1994	8.23882376306557
1995	8.020332906416929
1996	8.093981509781639
1997	8.000693278853007
1998	7.931954582379277
1999	7.841121304896134
2000	7.301277042232809
2001	7.497182327182939
2002	7.708308323495107
2003	7.680812844905615
2004	7.740959204320129
2005	7.858796969703665
2006	7.733348848639109
2007	7.661664208030791
2008	7.550945807639177
2009	7.52983320800796
2010	7.545790405403648
2011	7.519767898881449
2012	7.442191370003955
2013	7.453435056784301
2014	7.4534105072498456
2015	7.434988685785375
2016	7.416747080311971
2017	7.393300602213583
2018	7.36634329022193
2019	7.3776112609889335
2020	7.37947833353596
2021	7.373020770738734