Year	% of land area
1961	32.89018170402517
1962	32.94191396085593
1963	32.9797183023861
1964	33.01829641698852
1965	33.068481127674765
1966	33.0856146742747
1967	33.09224701489403
1968	33.21295561416579
1969	33.24025874971536
1970	33.16089174030407
1971	33.18543140059558
1972	33.21792986963029
1973	33.23351587008571
1974	33.1962950107117
1975	33.278242451176126
1976	33.36623928505889
1977	33.383374346933046
1978	33.44506056968
1979	33.54223295282441
1980	33.665273751959475
1981	33.65742478813325
1982	33.73624607275437
1983	33.84292565151927
1984	33.92738492424092
1985	34.02732102704245
1986	34.139528045121594
1987	34.14781920409296
1988	34.30590396848033
1989	34.349460190276574
1990	34.63401276617384
1991	34.82727437545463
1992	35.10840681511158
1993	35.30808337147266
1994	35.703432561923904
1995	36.11390584338775
1996	36.33868652565064
1997	36.542710523581164
1998	36.58277211031
1999	36.8124864190816
2000	36.92137176672438
2001	37.16609488623425
2002	37.290881471802315
2003	37.4809169690176
2004	37.41030556790017
2005	38.10099101459465
2006	38.130788798754786
2007	38.31190244511805
2008	38.4601697697711
2009	38.60099653097909
2010	38.75604343682911
2011	38.85329742708755
2012	39.0216572368552
2013	39.337175500620184
2014	39.42819304692354
2015	39.62502666436725
2016	39.72695565224889
2017	39.790277698551144
2018	40.003345361041276
2019	40.09738909193016
2020	40.172027973728724
2021	40.259361582476146