Year	% of land area
1961	42.775896500824864
1962	43.075453677172874
1963	42.775896500824864
1964	42.66301988365026
1965	42.606581575062954
1966	42.532777633064164
1967	42.54146044976991
1968	42.532777633064164
1969	42.41990101588956
1970	42.254927498480505
1971	42.23322045671616
1972	42.168099331423115
1973	41.92932187201528
1974	42.12468524789442
1975	42.289658765303464
1976	42.37214552400799
1977	42.46331509941825
1978	42.55882608318139
1979	42.619605800121555
1980	42.693409742120345
1981	42.75853086741339
1982	42.849700442823654
1983	42.99730832682122
1984	43.13189198576018
1985	43.34896240340366
1986	43.43579057046106
1987	43.761396196926285
1988	43.87861422245376
1989	41.23828210159146
1990	41.203400915631136
1991	41.065980998866905
1992	40.77834916761091
1993	40.70862023882158
1994	40.69103742756307
1995	40.68586866530132
1996	40.68055071453468
1997	40.71798893390842
1998	40.615880482599415
1999	40.644599303135884
2000	40.83844847851639
2001	40.79491532802229
2002	40.788271631791886
2003	40.778430093498585
2004	38.76086956521739
2005	39.06861466214453
2006	38.86859726932777
2007	37.73543868806821
2008	37.933884297520656
2009	38.203077458054416
2010	39.75657465768311
2011	39.079810574792546
2012	38.24884792626728
2013	38.02112767899839
2014	38.151947148817804
2015	38.151947148817804
2016	37.30006954102921
2017	37.130563282336574
2018	37.752086230876216
2019	38.969054242002784
2020	36.86978442280946
2021	37.32614742698192