Of the globe's three largest agency holding companies, two have now distanced themselves from one of the most common (and unreliable) indicators of future income - 'net new business' estimates.

Interpublic Group, during the throes of its ongoing financial travails, was the first to admit publicly that this sop to investors and analysts is not worth the paper on which it is written.

"I'm still amazed at the reliance placed in this industry on unsubstantiated and heavily hyped billings numbers as a measure of business vitality," said IPG chairman/ceo Michael I Roth during a recent conference call.

And earlier this week, Randall Weisenburger, cfo at world numero uno Omnicom Group agreed with Roth that "those numbers are not terribly meaningful". More significantly, he added that there is a "disconnect" between new-business numbers "and our revenue growth." However, the group will continue to provide such data "if asked".

Which, alone among the big boys, leaves WPP Group still flaunting new business values as guide to future performance. In its Q1 financial update earlier this week, WPP announced it had won new business to the tune of £875 million ($1.68bn; €1.28bn) during the quarter.

Some industry onlookers, including this scribe, have long been puzzled as to why credence has ever been attached to this hoary hoax?

The still widespread use of new business figures is "rife with estimate error," believes Tim Fidler, director of research at Ariel Capital Management, an investor both in IPG and Omnicom.. They are "a very crude measure at best," he opines.

Another haruspex, Alexia Quadrani of Bear Stearns, is sceptical of figures that don't accord with generally accepted accounting principles. "Generally speaking, there is a lot more pressure for companies to only give numbers that can be directly correlated back to GAAP," she says.

Sir Martin Sorrell, invariably good for a quote when invited, did not oblige on this occasion. WPP, when asked by the Wall Street Journal to comment on the credibility of new business figures, remained zip-lipped.

Adland cynics cite the time-hallowed formula: think of a number and double it. Like the blowfish, agencies (and clients) inflate to impress rivals, attract mates and deter predators.

Data sourced from Wall Street Journal Online; additional content by WARC staff