Recent figures on the difference between average men's and women's pay understandably caused outrage in some quarters.

The gender pay gap data published by the Government Equalities Office, showing men are paid on average 18% more than women, were 'a stark illustration of the fact that women’s labour is effectively treated, beyond a certain point, as slavery,' one commentator wrote in a national newspaper.

Local government was not exempt, although there may have been some consolation in the fact that its gender pay gap at around 5% was less than a third the national average across all sectors.

But while the figures clearly show there is a problem, there are some reasons for treating them with caution. Looked at closely, they reveal a somewhat more mixed picture of what is actually going on.

First, the data showed that at no less than a third of councils nationwide, women are actually paid more than men on average. There is a gender pay gap, but one that favours female employees.

As reported by LocalGov, Three Rivers DC in Rickmansworth, Herts, reported a mean average pay gap of 42% gap favouring women.

The council said this was because it had a large mainly male refuse collection workforce, on relatively low earnings, while several top jobs including heads of HR, housing, IT and finance, were held by women. The refuse service had been kept in-house, the council made a point of saying, rather than being outsourced as many other authorities had done in recent years.

For several other councils keeping lower-paid services in-house appeared to have had the opposite effect. At Lancaster City Council, the 4% pay gap in favour of men - rising to 15% on the more representative median average - was explained by the fact that cleaning services staff, mainly relatively lower-paid women, had been retained as direct employees.

This point was raised by the local government union Unison. The figures overall were rendered somewhat meaningless, the union's local government officer Heather Wakefield told LocalGov, because outsourcing of services by many, but not all, councils, meant that like was not being compared with like. If all council services had been taken together, regardless of who was providing them, the outcome might have been very different.

It must also be kept in mind that the figures are based on a snapshot of hourly earnings for all employees in all roles within a council. They do not reflect differences in pay for work of equal value - which is illegal.

Here again, however, it is what the figures do not show that may be important. As Unison also pointed out, current equality legislation does not allow jobs to be compared between different employers. An employee wanting to claim unfair discrimination must show that their work is of equal value with the work being done by an employee in the same organisation.

This means that where services have been outsourced, it is not possible for, say, a female cleaner at a council to mount a legal case that her work is of equal vale with that of a similar male worker in a service that has been transferred to the private sector.

Like private sector companies and other organisations, councils now have to collect detailed information on their pay strategies and will have to pay extra attention to discrepancies based on gender.

For a variety of reasons to do with good employment practice, the need to attract the best talent and to encourage a contented and motivated workforce, this must be welcomed.

The Government's gender pay gap survey, a pioneering exercise in statistical data-gathering, at least provides some facts on which to base future action.

The proof of just how useful the data is, however, will be determined by what changes take place in the months and years ahead.