Bad news is good news again, but for how long?

Talking heads have spent much of the past month reviving the

mantra that bad economic news is good news for markets, and vice versa. Their chorus reached fever pitch last week.

Deep breath now:

• Last week’s gloomy US and European PMI numbers suggest “a sharp downturn” in both regions, says Ben Seager-Scott of advisory group Evelyn Partners. “But bad news might be good news” if that means central banks no…