Statistics do not have the best reputation – often being equated with ‘damned lies’ – but they can be of critical relevance to employment proceedings. That was certainly so in one case concerning a part-time airline purser who was alleged to have been less favourably treated than her full-time colleagues.

The woman had worked full time in the past but had taken on a part-time role after returning from maternity leave. Her contract envisaged that she would work half as many hours as her full-time co-workers and would receive half their salary.

Full-time cabin crew members were required to be available for work for 243 days per year. Half of that was 121.5 days, but the woman had to be available for 130 days. On that basis, she complained that, when viewed proportionately, she was required to be available for 3.5 per cent more days than her full-time comparators.

In upholding her complaint, an Employment Tribunal (ET) found that, in requiring her to work an additional 8.5 days annually, without equivalent additional pay, the airline had breached the Part-Time Workers (Prevention of Less Favourable Treatment) Regulations 2000. The difference in treatment was in pursuance of a legitimate aim, but was not objectively justified in that the same operational objective could have been achieved by the simple, non-discriminatory, expedient of increasing her salary.

In ruling on the airline’s challenge to that decision, the Employment Appeal Tribunal upheld the ET’s conclusion that the woman had been less favourably treated. However, in allowing the appeal, it found that the ET was wrong to ignore statistical evidence put forward by the airline in support of its justification defence.

The airline had argued before the ET that it was in practice impossible to maintain absolute mathematical parity between the number of hours proportionately worked by the woman and her full-time comparators. Statistics showed that, during some periods, she worked longer hours than full-time colleagues and, in other periods, fewer. A broad approach to comparability was appropriate and any difference in treatment could be regarded as trivial or minimal. The objective justification issue was remitted to a freshly constituted ET for reconsideration.