Uselessness of the ISM

The closely watched economic indicator ISM is not as useful as many think. It is a survey of several business managers answering several questions. These managers have the incentive to make their businesses look better than they really are, so any optimistic looking ISM survey results should be taken in with a grain of salt. Also, they have nothing to do with the reality and nominal levels. It is a relative survey in the sense that the questions ask things like compared to last year is your business better, etc. It is the negative readings that matter more as they are very real. One should really disregard the slightly positive readings as they are misleading for investment purposes. I am not even going to mention the problems with data collection and manipulation in this survey. One point about this topic is the revisions to prior numbers. How can you revise answers to a survey of questions? What new data did these guys get to revise previous readings????