City building permit data- what trends should I look for?

[Richie Thomas]

I recently discovered that City-Data.com contains data on the # of single-family home construction permits issued over the last 20 years for many major and minor cities in the US.  For example, here's Bolingbrook, IL:

I'm showing it peaked in 2003 and then bottomed out over the next 5 years, and has stayed there ever since.  This is despite the permit cost in Bolingbrook being lower (sometimes significantly so) compared to the statewide average.  I'm assuming it's a negative indicator about the viability of this farm area, since builders are smart and go where the money is, and if the local market were strong then they'd build more homes.  My question is- how strong of a negative indicator is this?  Does anyone else use this as a signal when evaluating a farm area, and if so, how much weight do you give it?