FRANKFURT • Calling the top of the inflation wave has been a painful exercise for economists and central bankers, who have been proven wrong time and again over the past year.

But data on Wednesday showing that some inflation measures had cooled in the world's two largest economies is likely to rekindle a debate about whether the worst might be over.

US consumer prices did not rise last month from June due to a sharp drop in petrol costs, delivering the first sign of relief for Americans who have watched inflation climb in the past two years.

In addition, China's factory gate inflation slowed to a 17-month low on an annual basis, while consumer prices rose less than expected.

After wrongly predicting last year that high inflation would be transitory, most central bankers have stopped trying to put an exact date on when they expect current price growth to peak.

But Federal Reserve officials see inflation easing through the second half of the year, the European Central Bank puts the peak in the third quarter and the Bank of England sees it in October.

Here is some of the key data shaping the inflation debate:

RAW MATERIALS GETTING CHEAPER

The main culprit for the surge in consumer prices last winter - energy and other raw materials - may be the harbinger of lower inflation this time round.

Prices of many key commodities such as oil, wheat and copper have fallen recently, with a Refinitiv index spanning crude oil to orange juice down nearly 20 per cent from its May peak.

The fall mostly mirrors weaker global demand amid economic downturns from China to the United States and Europe, where consumers are struggling to cope with high prices.

This is already having an impact on some measures on inflation: The share of manufacturers reporting rising input costs is shrinking and growth in wholesale prices is slowing across much of the world.

This should eventually filter through to consumer inflation.

EUROPEAN ENERGY BILLS RISING

European households are unlikely to see energy bills come down any time soon and there is increasing talk of rationing in countries including in Germany.

This is because gas prices in Europe, which has for years relied on Russia for a large portion of its imports, are still four times higher now than a year ago and close to record highs.

Even in Britain, which has its own gas but very little storage capacity, consumers will see their power bills jump in October when price caps expire.

EXPECTATIONS (MOSTLY) UNDER CONTROL

Some central bankers can take comfort in the fact that investors have not lost faith in them.

Market-based measures of inflation expectations in the US and the euro zone are only just above the central banks' 2 per cent target, while they remain uncomfortably high in Britain.

Even the message from households, which are slower than markets in reacting to changes and tend to overestimate inflation, is not one of panic.

The vast majority of economists in a global Reuters poll also said it would be at least next year before the crisis recedes significantly, while 39 per cent thought it would take longer than that.

CORE PRICES MAY BE TRENDING DOWN

Measures of inflation that strip out energy and food prices have already started to fall in the US and Britain, and some predict Japan and the euro zone will follow suit.

Core inflation remains well above central banks' comfort zone across developed and developing economies, meaning that further policy tightening is needed.

But the latest slowdown in the US and Britain showed that the recent interest rate hikes were already having some effects.

An artificial intelligence model used by Oxford Economics suggests that core inflation will also peak in Japan and the euro zone in the second half of the year.

WAGES POINTING UP

Workers' wages have far from caught up with the increase in prices over the last year, but they are at least regaining some ground.

Unit labour cost, or the cost of labour for every unit of output, grew by almost 10 per cent for non-farm businesses in the US in the second quarter of this year, data showed earlier this week.

Wages are one of the most important drivers of prices in the long term and, if they rise too fast, they may initiate a vicious circle of price increases.

But outside the US, the rebound has been more modest and the upcoming recession may well weaken labour's hand in pay negotiations.

REUTERS