Year	% of land area
1961	16.077498300475867
1962	16.145479265805573
1963	16.145479265805573
1964	16.42873328801269
1965	16.42873328801269
1966	16.42873328801269
1967	16.440063448900975
1968	16.145479265805573
1969	15.578971221391344
1970	15.256061636075232
1971	10.197144799456153
1972	10.197144799456153
1973	10.197144799456153
1974	10.480398821663266
1975	10.480398821663266
1976	10.763652843870384
1977	10.763652843870384
1978	11.046906866077498
1979	11.046906866077498
1980	11.330160888284615
1981	11.330160888284615
1982	11.500113301608883
1983	11.556764106050306
1984	11.556764106050306
1985	13.029685021527307
1986	14.729209154769999
1987	16.995241332426918
1988	19.54452753229096
1989	20.875821436664403
1990	20.932472241105824
1991	20.960797643326533
1992	20.960797643326533
1993	21.051438930432813
1994	20.960797643326533
1995	20.960797643326533
1996	20.960797643326533
1997	20.960797643326533
1998	20.960797643326533
1999	20.960797643326533
2000	20.960797643326533
2001	20.960797643326533
2002	20.960797643326533
2003	20.960797643326533
2004	20.960797643326533
2005	20.960797643326533
2006	20.960797643326533
2007	20.960797643326533
2008	20.960797643326533
2009	20.960797643326533
2010	21.232721504645365
2011	21.5029107183322
2012	21.823998413777478
2013	21.9925458871516
2014	22.161092794017677
2015	22.329639700883753
2016	22.498187174257875
2017	22.666734081123952
2018	22.83528098799003
2019	23.00382846136415
2020	23.17237536823023
2021	23.340922841604353