The slowdown in Chinese growth, confirmed by last week’s third-quarter GDP report, is feeding fears that the world economy faces a prolonged period of stagnation, perhaps even a new crisis. In fact, China’s weakness is one of the reasons to be optimistic about global growth.

Of course, there are many reasons to be pessimistic too. Many emerging markets are in deep trouble. Many asset prices are unsustainably high. Seven years after the financial crisis erupted, major central banks are still forced to keep monetary policy at emergency settings. And the world is short of genuine consumer demand.

It is on this last score that China gives cautious grounds for confidence. Chinese growth of about 3 to 5 per cent as the economy weans itself off wasteful investment is exactly what the world needs. As the price of oil, copper and other commodities falls in response to China’s structural adjustment, demand deflates in countries that export energy and natural resources. Brazil and Russia, already deep in recession, will be among those watching anxiously for any economic policy announcements at this month’s plenary meeting of the Chinese Communist party.