Year	% of land area
1961	21.84557438794727
1962	21.980091471616895
1963	22.114608555286523
1964	22.168415388754372
1965	22.302932472423997
1966	22.437449556093625
1967	22.450901264460587
1968	22.58541834813021
1969	22.693032015065913
1970	22.652676889965026
1971	23.04277643260694
1972	23.44632768361582
1973	23.715361850955073
1974	24.01129943502825
1975	24.293785310734464
1976	24.576271186440678
1977	24.872208770513854
1978	24.885660478880816
1979	24.912563895614742
1980	24.95291902071563
1981	25.31611514662362
1982	25.746569814366428
1983	26.109765940274414
1984	26.446058649448478
1985	26.836158192090398
1986	27.17245090126446
1987	27.508743610438525
1988	27.845036319612593
1989	28.24858757062147
1990	28.57142857142857
1991	28.705945655098198
1992	28.9211729889696
1993	28.9211729889696
1994	28.71939736346516
1995	28.67904223836427
1996	28.67904223836427
1997	28.786655905299973
1998	28.907721280602637
1999	29.015334947538335
2000	29.99730965832661
2001	30.13720742534302
2002	30.102232983588916
2003	30.067258541834814
2004	30.03228410008071
2005	29.99730965832661
2006	29.921980091471617
2007	30.02152273338714
2008	29.986548291633035
2009	30.018832391713744
2010	30.486817325800374
2011	30.441216034436376
2012	30.306698950766748
2013	30.17218186709712
2014	30.126821370750136
2015	29.99190501888829
2016	29.856988667026446
2017	29.7220723151646
2018	29.56322458883796
2019	29.428417363170666
2020	29.308438932326773
2021	29.405715826368294