The underlying concept, which economists have referred to as agglomeration economies, dates back to 1890, and the work of Alfred Marshall.

(The elements of these which would reduce costs - such as the better transport system, the cheaper access to all kinds of services and so forth- are elements of agglomeration economies.)

More recently, high technology firms have concentrated largely along the M4 motorway, partly because of access to Heathrow Airport, but also because of agglomeration economies.

Economists such as Cameron (1980b) suggest a continuing 'fall in demand for urban agglomeration economies'.

Many special characteristics of cultural products - the lack of rivalry in content, economies of scale, and agglomeration economies - enhance the case for opening markets.

It is important to understand the possible ultimate outcome of agglomeration economies, only if the benefits outweigh the disadvantages.

The ultimate end to agglomeration economies is the formation and growth of a city.

Economies of scale external to a firm are the result of spatial proximity and are referred to as agglomeration economies of scale.

The ways of maintaining a stable outcome for agglomeration economies is for clustering to create "knowledge spillovers" that prevail over these negative externalities.

Forthcoming research for Defra on innovation illustrates how geographic clustering, even in rural settings, can bring some of the agglomeration economies enjoyed by urban businesses.