Most central banks do not wait nine years between changes in interest rates. But most central banks do not have economies like China's to deal with. The People's Bank of China raised rates by a strangely precise 27 basis points yesterday, the first move in nearly a decade.

That it chose to take this step was evidence that the measures taken by government to control China's surging economic growth earlier in the year had perhaps made less difference than it expected. But this interest rate rise is more symbol than substance.