Does size matter?
It's how big it is, not what you do with it. At least, that's the view of Britain's central bank.
I'm tempted to leave it there. But I suppose a little explanation might be needed.
You'll remember a couple of weeks ago I wrote about whether the Bank would continue its policy of quantitative easing. Back then, I said the answer might partly depend on whether you thought it was the quantity of new money created that mattered, or the process of injecting it into the economy.
If QE is a "topping up" exercise to bring nominal GDP - and the amount of money flowing the economy - back to normal levels, then what matters for the policy is how much you've put in.
If, on the other hand, you think of QE as an ongoing stimulus, you might be less interested in the size of the injection than in how it's being injected - and how long for.
You will find supporters of QE in both camps. But the minutes of last month's MPC meeting, published today, suggest that the Bank's policy-makers had a very clear view:
"The key question for the committee at the current meeting was whether it needed to make an immediate change to the total of planned asset purchases. It was important to recognise that the degree of monetary stimulus associated with the asset purchase programme was determined by the stock of the assets purchased rather than by the flow of purchases. Decisions on the appropriate degree of monetary stimulus would depend on the outlook for nominal demand and inflation."
So, size matters. QE is about how much money you inject into the economy - and how many assets you buy for that money - not how long you spend it for.
Does this help us establish whether the MPC will stop QE when it meets next month? Well, yes and no.
It does tell us that the best place to look for clues to that decision will be the Bank's expected path for cash GDP in the next year or two, not short-term developments in the asset markets.
On the basis of this statement, for example, I don't think we should expect the Bank of England to extend QE, simply to prevent further increases in long-term borrowing rates (notably the government's). If gilt yields rise, the MPC won't necessarily consider that a good reason to carry on.
To repeat and (grossly) oversimplify, if you think it's about quantities, that x amount of money is needed to get cash GDP back to normal levels, then once you've put x into the economy you should be unconcerned about what happens to bond yields after that. What matters is that the money is filtering its way through the economy.
That might lead you to conclude that the MPC is likely to give QE a rest in August. Or, as I suggested in that earlier post, to ease the markets' pain, it might say it will spend the last £25bn authorised by the chancellor, though more slowly than before.
Could it possibly be that simple? I suspect you know the answer. Because in this limpid description of the Bank's view of QE, I have left a small detail out.
Even if the MPC can agree that QE is about the quantity of money created - they don't actually have a clue what the right quantity is.
As senior figures at the Bank said at the time, the £150bn figure that was authorised by the chancellor when the policy began bore some relation to the shortfall in the broad money supply that the MPC was hoping to make up. But no-one knew how much they would actually need.
The Bank's critics - including Martin Weale at the NIESR, as it happens - have said that it has taken an overly mechanical, "monetarist" approach to QE in focussing only on the amount.
He and others would support a more Keynesian approach, intervening directly to support corporate debt markets, looking more at the direct effect on private lending rates than on how much money has gone in. As I noted last week, the IMF Board seems to agree.
On the basis of the minutes released today, this question was not even discussed in the July policy meeting. The debate was all about the scale of the asset purchases under QE, not the nature of the assets purchased or the way it is done.
Regardless of whether they opt to continue with QE next month, in putting quantity before quality some critics will say they have already made the wrong choice.