So far, nobody has pointed out that Miley Cyrus and Mark Carney have something in common, besides the same initials. Let me rectify this appalling omission.

The thing is, both have faced the same problem - of how to signal a break with the past, given their audiences' established priors.For Ms Cyrus, the problem has been to establish a break with her wholesome Hannah Montana image. For Dr Carney, it has been to show that the Bank is now more of a monetary activist, keen to use monetary policy to bolster the economy.

And both have faced the same twin dangers - of either under-signalling or over-signalling. For Ms Cyrus, an under-signal would have meant trading on her past and looking like a has-been. For Dr Carney, it would have meant not sufficiently changing rate expectations and hence the monetary stance. Equally, though, there's also been a danger of over-signalling: for Ms Cyrus, this lay in looking over-risque, for Dr Carney it meant the risk that a signal of low future rates is also a signal (pdf) of weak future activity, which could be self-fulfilling.

Herein, though, the similarity breaks down. Whereas Ms Cyrus has perhaps erred on the side of over-signalling - her performance at the VMAs has been widely criticised as sluttish, as if that were a bad thing - Dr Carney has under-signalled. As Andrew Lilico has pointed out, rate expectations have risen since he gave his "forward guidance" because the knock-outs gave markets the impression that the Bank actually cares about inflation.

I suspect their next major signals to reverse this pattern - for Miley to appear demure, in a "womanly" way, and (barring a postive growth surprise) Mark to dampen rate expectations.

If I had the expertise, I'd model this as an interated signaling game with the possibilities of the audience being non-Bayesian, either by over-reacting or under-reacting.

Instead, I'll make a cheaper point. It's that we should not, perhaps, criticise Dr Carney too much. To have made an effective stimulatory over-signal, he would have had to say: "The economy looks like recovering nicely, so don't hold back spending for fear of recession, but even so I'll not raise rates." But the fact that the inflation target still exists rules this out. In this sense, pop stars have fewer constraints upon their judgment than central bankers.