If Greensboro's Assessed Valuation per Square Mile only went up 1.84% from 2006 to 2012...?

http://www.greensboro-nc.gov/modules/showdocument.aspx?documentid=17239

...why did Guilford County Property Tax Assessments on residential real estate rise 1.5%, after housing prices crashed?



Source: Don Jud, UNCG

Notice the 2006/2007 home prices were by far higher than at any time since the 1990's.
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"Greensboro’s available property valuation growth, measured both in terms of per capita and per square mile, is the lowest among peer cities for FY 2011-2012 compared to FY 2006-2007.

...assessed value of all taxable property per square mile has only increased by 1.8% compared to peer cities that have seen increases of 8-42% in FY 2011-2012 versus FY 2006-2007. In FY 2011-2012 the City of Greensboro had the second lowest assessed valuation per square mile of all the comparison cities and the lowest percentage increase of assessed valuation per a square mile of all five cities."

http://www.greensboro-nc.gov/modules/showdocument.aspx?documentid=17239
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If Forsyth County/Winston Salem, North Carolina's tax assessed values fell about 8% between 2009 and 2013, how did Guilford County/Greensboro values rise 1.5% between 2004 and 2012, as the City of High Point's property assessments fell 3%?