One of the first rules of drug dealing is, as Elvira Hancock said, "don't get high on your own supply." Two things I've seen today suggest that journalists should aspire to the higher standards of drug-dealers.

First, Allister Heath says it is "no longer tolerable" that the ONS revises its initial estimates of GDP so much. He says of the first estimate that GDP fell 0.7% - since revised to 0.4% - in Q2:

The impact on politicians, economists and corporate executives who obsess about the minutiae of these figures will have been significant. CEOs may have delayed investment plans on the basis of flawed figures.

This is tosh. The reaction of many economists to that first estimate was simply not to believe it. And whilst I have a lower opinion of CEOs than most, even I don't think they are so imbecilic as to base investment plans on GDP numbers (clue - time moves forwards, not back).

In fact, the ONS told us not to believe it.It accompanied the number with a table showing that the first estimate of quarterly GDP growth is revised by an average of 0.3 percentage points. And it said its Q2 estimate "may be subject to greater uncertainty than usual."

Such revisions are, in truth, inevitable. A ''1.5 trillion economy cannot be measured quickly and accurately.

The only people who can possibly be remotely upset by the ONS's revision are those journalists who got high on their supply - who were daft enough to believe their information suppliers.

Which brings me to my second example - Kelvin Mackenzie's account ('') of his part in the Hillsborough libels. He asks: "Why shouldn't I believe what four senior officers had told the partners of a local news agency?"

Simple. Whilst the police have little incentive to lie in the normal course of duty - when they are telling journalists about crimes by other people - they have every incentive to lie when trying to distract attention from their own murderous incompetence. Econ 101 should have told Mackenzie to be sceptical.

But he wasn't. If we are to believe him (and I'm not sure we should, but let that pass) he got high on his supply.

Of course, it's entirely reasonable - correct even - for journalists to report economic statistics and the words of policemen. It is, however, another thing entirely to believe them.

My point here is not merely about Mackenzie and Heath. It's about journalism generally. I suspect that, quite often, the reporting of the words of "senior" people - not just policemen but also politicians and businessmen - becomes the believing of those words, or at least the insufficient scrutiny of them. And this helps to support those in power, even if they are downright dishonest.