If it is really true that only one council worker in four joined in yesterday's pensions strike, it could be because they are rather shrewd, or somebody has been passing round sound advice.

At first sight, these council people have an appealing case. The Government caved in pathetically when the civil servants threatened to strike rather than work on till 65 to rank for a full pension. Why on earth should their counterparts in local government be treated worse?

If council taxpayers cannot afford it, then let the Government stump up to right an injustice of its own making.

Or so I was thinking yesterday morning listening woozy-headedly to BBC 4's "Today" programme. Then I heard Dave Prentis, who runs Unison, Britain's biggest union, let drop that his members' pensions average just £31 a week.

How much of it, I wondered as I woke up, does Gordon Brown take off them with his pension credit means test?

You guessed. None of the very helpful people I could find in the Department of Work and Pensions was quite sure of the numbers. The nearest they came to a reassurance was the verdict from t he Financial Services Authority when pension credits started in 2003 - "For most people, most of the time, it pays to save".

How much it pays is harder to assess. The numbers go something like this. From April 6 the basic state pension for a single person will be £84.25 a week. Anybody with nothing else at all gets a "guaranteed" credit to bring their income up to £114.05 - an extra £29.80. Sadly, this is wiped out by a £31 a week local government pension, leaving the pensioner a slender £1.20 better off.

To make up for that, there is a second element of pension credit for people with "modest" savings or occupational pensions. What "modest" amounts to is unclear. Anyway, this savings-linked credit apparently cannot be worth more than £17.88 a week. So supposing our pensioner does qualify for that maximum, he or she will be left with £19.08 of the original £31 a week.

That is if I've got all the numbers right. They are the outcome of several conversations with a recurring theme that every case is different. The DWP's internal booklet spelling out the rules is 60 pages thick. Just how pensioners can tell if they have been awarded the right amount is not revealed.

But allowing for all the "ifs" and "maybes" it looks as if yesterday's strikers have less to lose than they may have supposed.

That, remember, is with a copper-plated final salary scheme - regardless of the age at which it starts. More than three million people draw pension credits.

Two-thirds of them, it is said, have been lifted out of "absolute poverty", at a cost which Gordon Brown finds affordable.

Still, it amounts to one more reminder of how hard it has become for anybody with less than average earnings to accumulate a money purchase pension that gives them fair value allowing for the credits they stand to lose - supposing always that Gordon's means test survives his Chancellorship.