Equal pay remains an issue in modern Scotland, mystifying economists and commentators alike. It is hard to believe, after a generation of social change, that many thousands of women are still fighting to be paid the same as men.

The issue seems to apply across the social scale, perhaps for different reasons. There are plenty of theories as to cause but it seems downright strange, for example, that average salaries for women in the legal profession are 42 per cent lower than for men, as the Law Society of Scotland has reported.

The average difference is more than £32,000, which tells us something about the comfortable salaries enjoyed by many lawyers. For women still fighting for equal pay in ordinary jobs, many of them employed by councils, £32,000 is an annual income about which they can only dream. Nevertheless the glaring gender disparity remains, regardless of class and income.

This year 4,000 female current and former employees of North Lanarkshire Council – cooks, cleaners, home carers and catering staff – agreed a £70 million settlement after a 10 year campaign. Glasgow City Council is currently engaged in similar equal pay cases involving several thousand women.

At a time when awareness of equality issues is high, and where there appears to be political consensus about transforming child-care provision in Scotland, the economists at Fiscal Affairs Scotland (FAS) have discovered that, according to the Office of National Statistics (ONS), the gender pay gap in Scotland worsened during the three years to 2014; even though Scottish performance was better than in the other nations of the UK during 1997-2011.

The question is why that might be, and we are not too clear on that, other than to speculate that old habits die hard in the Scottish workplace.

John McLaren of FAS postulates that older women – over 40 – have the worst of the problem. The gender gap in pay has narrowed to just 10 per cent for women aged 35 and under. But it broadens to 30 per cent at age 40 and 40 per cent at 50. These latter figures are not a lot different from the average of 50 per cent that prevailed 40 years ago.

This indicates that younger women may be more skilled and in “better” jobs, entering the labour market since equal pay has been addressed more seriously by employers. And, as women are having fewer children and starting families later in life than in the 1970s, they are enjoying higher pay than older women, or those who took career breaks to raise children in the past.

Forty years ago, there were seven times more children born to women under 25 than to those aged more than 35. Today the birth rate for both groups is virtually the same. It is within statistics like these where we might discern the different experiences of younger and older women in terms of work status and pay.

The Scottish Government launched a “women’s pledge” on gender equality, including pay earlier this year. The First Minister and the leader and acting leader of two opposition parties are female. We can assume that all three share strong views on equal pay and other measures that deliver equality as well as – it is to be hoped – real economic growth.

Last month, the UK Government announced that businesses employing more than 250 people will be obliged to publish wage data by gender. Perhaps the only way to achieve change is to embarrass employers in public.

Curiously, equal pay remains a reserved power, and was not included in the Smith Commission’s all-party shopping list of responsibilities to be passed to the Scottish Parliament. Perhaps there is time for a suitable amendment.

Equal pay first appeared in a Labour Party manifesto at the 1959 election campaign. It won TUC support in 1965, three years before the celebrated Ford machinists’ strike at Dagenham, and five years before the Equal Pay Act arrived in 1970.

Yes, that last date was 1970; 45 years ago; not a misprint.

There is no doubt that male and female career patterns are different, partly out of social tradition, childbirth and so on.

But one interesting statistic from ONS seems to indicate that the trend of change continues: Northern Ireland, for long the most socially conservative part of the UK, is now the only one where the gender pay gap actually favours women.

Employers, including local authorities, need to address the situation in Scotland. And surely this is one issue where our major political parties can agree to a loud and powerful public campaign on pay.