This week's claims of thousands of teacherless classrooms sends the Diary hurrying to that DFEE bible, Statistics of Education, 1998 Edition (pound;14.95 from the Stationary Office and worth every penny if 71 pages of close-printed figures are your thing).
There, we are alarmed to find - Blimey! - 4,519 teaching vacancies last year, more than double the year before. Worst of all, 3,000 of them are in London. (Table 40, if you're checking).
And yet ... somehow the figures don't quite add up. Tally the next two tables in the book, which split primary and secondary, and you only get 2,500. And how come the London total is so high?
There's a simple answer, but it's not very reassuring. Those bright boffins in Sanctuary Buildings have added the year into the London totals. Deduct 1,998 from last year's figure and you may get somewhere near the truth.
There are statistics, damn statistics, and then there is the DFEE.