Year	% of land area
1961	21.90545303752851
1962	21.573709309558367
1963	21.77068214804064
1964	22.71407837445573
1965	23.61600663487456
1966	23.999585320340035
1967	24.217292141820444
1968	24.289861082313912
1969	24.22765913331951
1970	24.092888243831638
1971	23.833713456354964
1972	23.53307070288202
1973	23.54343769438109
1974	23.51233671988389
1975	23.55380468588016
1976	23.53307070288202
1977	23.50196972838482
1978	23.460501762388557
1979	23.34646485589882
1980	23.294629898403482
1981	23.273895915405348
1982	23.253161932407217
1983	23.180592991913745
1984	23.10802405142028
1985	23.014721127928674
1986	22.983620153431474
1987	23.00435413642961
1988	22.95251917893427
1989	22.776280323450134
1990	22.58967447646693
1991	22.403068629483723
1992	22.14389384200705
1993	21.957287995023844
1994	21.72921418204437
1995	21.231598590089156
1996	20.816918930126477
1997	20.557744142649803
1998	20.412606261662866
1999	20.25710138917686
2000	20.454074227659135
2001	20.10543725449659
2002	19.82642835003616
2003	19.64876033057851
2004	19.55174550712663
2005	19.42178626742385
2006	19.17836498761354
2007	18.984729673957904
2008	18.73389009176204
2009	18.49371522769421
2010	18.24074074074074
2011	18.068731350962032
2012	18.374267803925598
2013	18.154291462238007
2014	17.944165041568304
2015	17.815177792600952
2016	17.446070838761297
2017	17.195159470823505
2018	16.94011484823626
2019	16.772540983606557
2020	16.608606557377048
2021	16.424180327868854