Year	% of land area
2006	29.67871026755088
2007	29.919963411845412
2008	30.41962039789618
2009	29.88451863709124
2010	30.348730848387834
2011	30.17951063343243
2012	29.29453464440887
2013	29.616967756688773
2014	29.793048250628857
2015	29.62497141550423
2016	29.70500800365882
2017	29.67070660873542
2018	29.533501029041847
2019	29.48776583581066
2020	30.96682126293257
2021	31.0976334879296