When they eventually receive their voting slips, Unison members will have to decide whether or not to vote for "a campaign involving substantial and sustained industrial action, starting with a two-day strike", which the union considers the only way local government employers can be persuaded to increase their final pay offer of 2.475% plus £6 per hour (3.4%) on scale point 4.

While campaigning very strongly for a yes vote, the union is unsure about the outcome of the ballot. There are many factors that could affect their members' decision. But for many people there will be a fairly simple calculation. The reasoning goes like this:

• First, there will be no strike pay and those taking part in any action will not be paid for days spent on strike.
• Second, the difference between the unions' claim of 5% or £1,000 and the employers' final offer of 2.475% is worth around 2.5% to most staff.
• So, third, how many days' pay do I have to lose before any gain from a maximum extra 2.5% is wiped out by my lost earnings? Answer, not much.

Once you have been on strike for more than two or three days, it is unlikely than any improved offer will be enough to offset the lost earnings due to taking strike action. This is the reality of striking over pay in a low inflation environment, where the difference between the unions' and the employers' final positions can be counted in low single percentage points.

Of course, other factors could influence the vote. For example, some might believe that simply voting "yes" will be enough to persuade the employers to up their offer, without any strike action taking place. But Unison has made clear it does not believe the employers can be budged by the mere threat of strike action, which is why it is telling members:

"you will be asked to vote 'yes' on the basis that you are prepared to take part in all-out, escalating strike action, starting with a two-day strike"

This decision will not be taken lightly by people who understand that in all likelihood they will lose money even if they "win" the dispute.

Another possible reason for voting "yes" would be a general feeling of anger and demoralisation and desire to send a message to the employer. There is no doubt that such feelings exist in significant parts of the local authority workforce, but are a majority of union members angry enough to risk losing money in order to make their point?

There is an additional reason why people may be persuaded to vote "yes": the belief that the action will be part of a bigger co-ordinated campaign on public sector pay.

Last month, the Trades Union Congress passed a motion backing co-ordinated industrial action on public sector pay.

"Congress believes that the [public] sector-wide pay freeze has created the conditions for another co-ordinated campaign including industrial action if necessary. We note that affiliates have been holding discussions on such a campaign since the Spring."

Inevitably, the press duly reached for the industrial relations cliché handbook. As the Guardian put it, for example: "The threat of a winter of discontent under a Labour government increased today as TUC delegates backed coordinated industrial action over public sector pay."

So what are the chances of a co-ordinated campaign of strike action on public sector pay this winter? In my view: close to zero.

Why? For a start, millions of public sector workers, including some traditionally more stroppy groups such as the firefighters, have already settled on pay for 2007.

NHS workers, in particular, have overwhelmingly backed a pay offer in a ballot whose result was announced during the week of the TUC Congress.

So for what it's worth, I don't predict a riot on public sector pay this winter. Expect either a "no" vote in the Unison ballot or a very small majority for strike action.