In the 1920s the parents of Eduardo Luigi Paolozzi had emigrated from Italy to Leith, in Scotland, where they set up an ice-cream parlour.

ECONOMIST: Obituary

To give a simple example: if two shrewd, competing ice-cream sellers share a long beach, they will set up stalls back-to-back in the middle and stay put, explains Stephen Black, a modeller in the firm's London headquarters.

ECONOMIST: Modelling behaviour