Year	% of land area
1961	15.46738399462004
1962	15.46738399462004
1963	15.46738399462004
1964	15.46738399462004
1965	15.46738399462004
1966	15.46738399462004
1967	15.601882985877605
1968	15.601882985877605
1969	15.66913248150639
1970	16.34162743779422
1971	16.34162743779422
1972	16.47612642905178
1973	16.812373907195695
1974	16.812373907195695
1975	17.14862138533961
1976	17.350369872225958
1977	17.61936785474109
1978	18.224613315400134
1979	18.560860793544048
1980	18.762609280430397
1981	18.964357767316745
1982	19.09885675857431
1983	19.233355749831876
1984	19.435104236718225
1985	19.636852723604573
1986	19.83860121049092
1987	20.107599193006052
1988	20.376597175521184
1989	20.51109616677875
1990	21.385339609952926
1991	22.19233355749832
1992	22.19233355749832
1993	22.528581035642233
1994	22.864828513786147
1995	22.864828513786147
1996	22.999327505043713
1997	23.066577000672496
1998	22.93207800941493
1999	22.6630800268998
2000	22.6630800268998
2001	22.636180228648286
2002	22.609280430396772
2003	22.447881640887694
2004	22.42098184263618
2005	22.394082044384668
2006	22.367182246133154
2007	22.34028244788164
2008	22.649630127774042
2009	22.757229320780095
2010	22.73032952252858
2011	22.77067921990585
2012	22.80430396772024
2013	22.837928715534634
2014	22.871553463349027
2015	22.905178211163417
2016	22.938802958977806
2017	22.972427706792196
2018	23.00605245460659
2019	22.958977807666443
2020	22.958977807666443
2021	22.958977807666443