Reference cost data that should reveal all never discloses full story

The NHS's reference costs, published last week, now cover 'more cost data than any other reporting system anywhere in the world', according to health minister John Denham: more than 69 million hospital episodes or two-and-a-half times more data than for 1998-99.

Quite an achievement. What a pity, then, that the overwhelming impression is of hidden truths. One of the most expensive trusts claims incorrect data is responsible for its unenviable position; one of the least expensive readily admits that many more factors are at play than simply sound financial management.

Ministers exhort trusts to 'continually investigate' cost variations. And so they should.

But it is hard to resist the conclusion that any manager worth their salt will have a battery of plausible explanations ready to meet most awkward questions arising from these figures.