Year	% of land area
1961	27.731930213237334
1962	27.63961968060556
1963	27.515000461552663
1964	27.58054093972122
1965	27.61469583679498
1966	27.64792762854242
1967	27.682082525616174
1968	27.71531431736361
1969	27.934090279700914
1970	27.967322071448354
1971	28.370719099049204
1972	28.865503553955506
1973	28.900581556355583
1974	29.39444290593557
1975	29.89015046616819
1976	29.923382257915627
1977	30.419089818148247
1978	30.452321609895687
1979	30.947106064801993
1980	30.98126096187575
1981	31.476968522108372
1982	31.51112341918213
1983	31.54527831625589
1984	32.04744761377273
1985	32.019754453983204
1986	32.49607680236315
1987	32.51823133019477
1988	32.53946275270008
1989	32.74254592448999
1990	32.72869934459522
1991	33.04347826086956
1992	33.07578694729069
1993	33.42841318194406
1994	33.55580171697591
1995	33.78565494322902
1996	33.86319579063971
1997	34.03858580264008
1998	34.1382811778824
1999	34.21859134127204
2000	34.28690113541955
2001	34.298901504661686
2002	34.44198283024093
2003	33.82904089356595
2004	33.801347733776424
2005	34.11981907135604
2006	34.24582294839841
2007	34.33582571771439
2008	34.41475122311456
2009	34.49367672851472
2010	34.57260223391489
2011	34.65706637127296
2012	34.746146035262626
2013	34.836148804578606
2014	34.846157851010794
2015	34.8470741253577
2016	34.879748084556454
2017	34.774805224776145
2018	34.96409055663251
2019	35.07377633157943
2020	35.08508640265855
2021	35.18819089818149