The river is silted up and the water flows sluggishly.

The same sort of lag occurred with the introduction in the 1970s of emission controls on cars.

News of U.S. credit rating downgrade highlighted their concerns about the sluggish economies in their primary export markets.

He reckons investors are at the early stage of a bull market, although sharp move upwards are unlikely given sluggish growth.

But Fed purchases might only work if inflation were still low and the economic recovery sluggish.