A couple of interesting pieces Out There about housing inventory. Keep in mind as you read them, of course, that so much about inventory is estimates; take it all with a grain of salt.

First there’s good ol’ “shadow inventory,” aka the foreclosure pipeline: homes that are not on the market yet, but are in or near foreclosure and thus will soon be available. There is much hand-wringing about how this lurking wave of distressed property will affect the rest of the market.

The problem, though, is that there isn’t an official definition of “near foreclosure.” As a Wall Street Journal story points out, how much is coming down the pike depends on who you ask. In the paper’s quick survey, the numbers ranged from CoreLogic’s guess estimate of 1.6 million homes to Amherst Securities’s 10.3 million guess estimate.

Why the range? Because you’re trying to guess how many homes will be in foreclosure based on things like “days past due” that are far from reliable indicators.

So why should you care about shadow inventory? Because foreclosures (as we know) can play havok with property values. The more distressed sales that come out of the shadows, the greater the impact on existing prices.

It’s like trying to guess the size of the earthquake so you can decide how big a tsunami is coming. (But you don’t have a seismograph, and there are a lot of other factors that will determine the tidal wave’s power.)

But wait, there’s more!

So you’ve got all these foreclosures in the pipeline. Some of them take months, some take years (and some will never happen). Now add the fact that the foreclosure process across the country ground to a halt when lenders were caught with the whole fake paperwork, forged signature, robo-signing mess. Those homes will eventually make it back into the system, adding power to the forthcoming wave.

Meantime, because lenders are being careful (and legal) this time, foreclosures are taking a lot longer than they had been.

Some people say we need to speed up the foreclosure process — let’s get this mess over with (and the market back to ‘normal’) ASAP. Others point out that that lenders have shown they aren’t exactly trustworthy, so we need to make sure things are kosher before we kick people out of their homes.

And the Fed says that A) unnecessary foreclosures are hurting the market, and B) we need to put foreclosed homes back on the market slowly to avoid a shock to the system.

Messy, huh?

What’s the bottom line? Prices have been falling. The shadow inventory will eventually — quickly or slowly — see the light of day. That will probably push prices down, but it’s impossible to say whether it will be by a lot or a little.

How’s that for a Monday afternoon reading list?