Year	% of land area
1961	15.233989508128603
1962	15.233989508128603
1963	15.753389082220954
1964	15.753389082220954
1965	16.267594660572378
1966	16.267594660572378
1967	16.78699423466473
1968	17.6647795148808
1969	16.55326442632317
1970	16.350698592427154
1971	16.77141224744196
1972	16.77141224744196
1973	17.03111203448813
1974	17.29081182153431
1975	17.285617825793384
1976	17.27522983431154
1977	16.226042694644992
1978	16.220848698904067
1979	16.215654703163143
1980	16.210460707422218
1981	16.205266711681297
1982	16.194878720199448
1983	16.184490728717602
1984	16.174102737235753
1985	16.15332675427206
1986	16.13774476704929
1987	16.12216277982652
1988	16.09099880538098
1989	16.070222822417286
1990	16.059834830935436
1991	15.441749337765543
1992	15.81052303537111
1993	16.007894873526205
1994	16.50651846465486
1995	15.981924894821587
1996	16.709084298550874
1997	15.259959486833221
1998	13.945878564379576
1999	17.69594348932634
2000	17.254453851347844
2001	16.0961928011219
2002	15.841687009816653
2003	15.22879551238768
2004	15.514465278138474
2005	16.236430686126837
2006	14.740559912740872
2007	14.802887861631952
2008	18.802264582143042
2009	18.802264582143042
2010	18.802264582143042
2011	17.140185945047527
2012	17.140185945047527
2013	17.140185945047527
2014	17.140185945047527
2015	18.984054433075364
2016	18.750324624733807
2017	18.93211447566613
2018	19.11390432659845
2019	19.295694177530777
2020	19.477484028463095
2021	19.893003687736975