As the European Central Bank gets ready to raise interest rates in the euro zone, two international organisations, the OECD and the IMF, believe it is about to make a mistake.
Beyond the independent ECB's resentment of outside advice, the disagreement shows the extent to which monetary policy is more of an art than a science.
At issue is whether the output gap - the difference between what an economy produces and what it is capable of producing - should be used as a tool to gauge when there is a real inflation risk that requires remedial interest rate rises.
It should, according to the International Monetary Fund and the Organisation for Economic Co- operation and Development, both of whom recently urged the ECB to hold fire on rates until it has surer proof of economic recovery in the euro currency area.
Their bottom line is that an economy which has underperformed for a period has built up slack, a "negative output gap" which takes time to work itself off even after the economy returns to higher growth rates, as it seems to be doing.
That is why OECD chief economist Jean-Philippe Cotis urged the ECB last week to avoid raising rates until about October, when it will have harder evidence of how strongly the economy is rebounding from a largely unexpected dip at the end of 2005.
IMF chief Rodrigo Rato also repeated publicly that the ECB should wait until it is sure of recovery.
Even if the economy is now running again at full capacity - generally estimated to be growth of about two per cent - disinflationary pressures are still at work and will be for some time, the organisations argue.
The OECD estimates that the output gap is negative in the euro zone and will only narrow to 1.4 per cent of gross domestic product this year from 1.6 per cent of GDP in 2005 - implying there is still a lot of slack and disinflationary forces are still at work.
The ECB, which financial markets are convinced will increase rates at a meeting in Madrid on Thursday, begs to differ, however, on the grounds that the output gap is simply too hard to measure reliably.
ECB President Jean-Claude Trichet spelled out his distaste for it at a US central bank conference in Wyoming last August where he referred to the "spectacular policy mistakes" of the inflation-scarred 1970s.
"Advances in economic theory since the 1970s and more sophisticated econometrics have not immunised the policy process from these potential pitfalls," Mr Trichet said, citing erroneous output gap estimates in particular.
He seems to have a point. Back in 1999, during what turned out to be the middle of the last boom period, OECD and IMF estimates showed negative output gaps, implying that the economy was running well below capacity.
A few years later, those figures were revised to the extent that what had initially been depicted as a negative output gap turned out in reality to be a positive one. Original estimates were drastically wide of the mark, Mr Trichet pointed out.
Daniel Gros, economist director of the Centre for European Policy Studies in Brussels defends Mr Trichet's stand.
"The ECB was more cautious then and it's more cautious now, " he says approvingly.