Meanwhile, Dr Forrest's group has constructed an experimental set-up, described in a paper recently submitted to the Evolutionary Computation Journal, that mimics the way real immune systems identify invading pathogens.

ECONOMIST: A thousand ills require a thousand cures

First, if universities are to create centres of excellence they will need greater freedom: for example, to recruit their staff, to set up experimental links with research bodies or to increase enrolment fees.

ECONOMIST: In higher education, a free-for-all does not work

Moreover, in the few areas of America where one cable company has built over a rival's existing system, where a telephone company has set up an experimental system to deliver television signals, or where there is an old, municipally owned cable system as well as a private one, competition has led to lower prices (see chart).

ECONOMIST: Cable��s hold on America