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.
"HTC does not report their shipment numbers," Dediu notes. "It stopped some time late last year. Neither does Motorola now that it’s a part of Google. Huawei is silent except for setting targets and ZTE published a press release citing IDC’s estimate of its own shipments.
"But most glaring of all is the absence of any mention by Samsung of its performance. The company stopped reporting any data on either overall phone shipments or of smartphones within that total since Q3 2011. We may have been able to estimate Samsung if we had more competitor actuals, allowing us to back into a figure. But we don’t."
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.