At one recent gathering, Mr. Buiter opined on the disastrous effect rising health care costs would have on the labor market.

WSJ: Citi's Provocateur in Residence

In early May the business and public-policy worlds awoke to the gathering trouble over the rising value of the euro and its further enervating effect on Germany and France, in particular.

FORBES: The Other Problem

The filters might be great for users, but they could have a negative effect on companies that have sunk money into promoting their pages and gathering fans, said one analyst.

CNN: Facebook revamps site, tweaks mobile apps

In all three cases, explained Dr Stysley, the effect is a small one - but it could in some instances outperform existing methods of sample gathering.

BBC: Nasa examines 'tractor beams' for sample gathering