"The risk factors include the dimensions of the structure, its location and its location relative to other buildings around it, " explains Matthew Waldrum from Omega Red Group, who assesses the risk of lightning hitting buildings.

BBC: What is the chance of lightning striking St Peter's?

Many firms now know that it offers more flexibility than proprietary programs, the licences for which often include restrictions on how they can be used, explains Matthew Aslett, of the 451 Group, a market-research firm.

ECONOMIST: Open-source software in the recession: Born free | The

"It would take three or four hours to clear a ridge line so soldiers could advance, " explains Lieutenant Colonel Matthew England of the Army's training and doctrine command, which develops equipment for soldiers.

FORBES: Companies, People, Ideas

In a 2009 paper Mr Glaeser and Matthew Resseger of Harvard University find that in highly skilled areas, city size explains 45% of the variation in worker productivity (it has almost no effect in underskilled cities).

ECONOMIST: Free exchange