FORTUNE — Can you spot what’s wrong with the spreadsheet at right issued Tuesday by Gartner, Inc?
No, it’s not the fact that it shows the worldwide market for mobile phones shrinking by 2.3% year over year. Or the rapid growth in Samsung sales. Or, say, the comparatively slow growth for Apple’s (AAPL) iPhone?
No, what’s wrong with Gartner’s spreadsheet — and a similar one issued a week earlier by IDC — is that they give the impression that these figures are accurate to 1,000 or even 100 units.
But as Asymco‘s Horace Dediu points out, that’s impossible. Because except for Apple, Nokia (NOK) and Research in Motion (RIMM), none of the companies listed above have released any information about their mobile phone sales.
It would be one thing if Gartner’s or IDC’s estimates proved accurate in retrospect when compared with numbers extracted from the companies as part of legal proceedings. But as we saw last week, that hasn’t been the case.