Year	% of land area
1990	68.89335854079532
1991	68.91790807525021
1992	68.94245760970512
1993	68.96700714416002
1994	68.99155667861491
1995	69.01610621306983
1996	69.04065574752472
1997	69.06520528197963
1998	69.08975481643454
1999	69.11430435088944
2000	69.13885388534435
2001	69.11675930433493
2002	69.09466472332552
2003	69.07257014231611
2004	69.05047556130668
2005	69.02838098029727
2006	69.00628639928786
2007	68.98419181827845
2008	68.96209723726903
2009	68.94000265625962
2010	68.91790807525021
2011	68.8722459411641
2012	68.82658380707797
2013	68.78092167299185
2014	68.73525953890574
2015	68.69449813537894
2016	68.69449813537894
2017	68.69449813537894
2018	68.69449813537894
2019	68.69906052438793
2020	68.69907030761067
2021	68.69906895820047