Published: 03/11/2005 Volume 115 No. 5980 Page 34

The old Marxist analysis of the capitalist salary strategy was that the successful mill owner drove workers to maximise efficiency. Employees were always on the verge of starvation, but paid just enough to keep going.

It didn't make financial sense to pay them so badly that they were too starving to work, but it wasn't economically sensible to pay them any more than necessary.

We may have thought this nightmare scenario had no relevance today. But an economist at Ohio's Bowling Green State University has published a mathematical model of modern day salaried professions that suggests the analysis has renewed relevance.

It suggests that those working in competitive areas inevitably toil on the verge of depression or burn-out, much as wage workers once toiled on the edge of starvation.

Alan Day Haight, the economist advocating the model's application to financial services workers, points out that workers in professions such as accounting and law are motivated largely by hope of advancement. Since they accept hope as payment, senior partners get more work out of them than they are paid for.

Haight reminds us that, typically, senior professionals benefit from juniors' long hours. Rivalry enhances the diligence of younger professionals, so the partners have an incentive to hire more than one for each anticipated promotion. But how much more?

The model suggests an answer that may ring true to many workers: there is enough rivalry only when the juniors are suffering from so much promotion anxiety that they are always on the verge of giving up or burning out.

With the same number of donkeys chasing the equivalent carrots, no unpaid hours would be offered and juniors would coast to promotions.

However, rivalry is an effective catalyst for diligence only when success is reasonably possible.

Haight's model shows, in a volatile market, judging the amount of staff to hire or lay off requires anticipation of when economic conditions create the right balance of staff morale and effort.

Dr Raj Persaud is consultant psychiatrist at South London and Maudsley trust and professor for public understanding of psychiatry.