Technology exists to show the actual short volume
Post# of 72440
That would be a good reason for some of these "wash trades" that Alan refers to -- they are trades at exactly the same price, with the same number of shares. Close one short, then re-open it so that you can manipulate the short interest figures.
If they had to report the short interest every day they couldn't get away with that. But golly, the SEC doesn't think that is necessary. I wonder why.