I figure anything that will generate a negative balance might possibly
allow you to ship out of stock.
Not only do you have inaccuracies counting when stuff comes in and out,
(possible gauge recalibration), you may also have environmental factors.
Ever notice a clothes line change tautness depending on the humidity and
other weather factors? Or, if you measure bread dough by volume before
and after the rising process?
A lot of old stuff just went under the trust method. "Heck, we don't want
to slow down getting stuff out just because the inventory hasn't been
received yet. What do you mean I can't ship 200,000 sand bags to the
levee where the flood waters are rising until they've been received? You
go tell that to the company of national guardsmen outside the gate."