I agree with Mario that *district* is the word, but I think *realtà* requires a little recasting

http://www.findarticles.com/p/articles/mi_qa3671/is_200107/a...
**Industrial districts** are geographically defined production systems characterized by a large number of small and mediumsized firms that are involved in various stages of the production process in a particular industry

You could say something like
**The/these industrial districts, defined as clusters of industrial enterprises...**

--------------------------------------------------
Note added at 2 hrs 15 mins (2005-09-28 21:56:29 GMT)
--------------------------------------------------

as for your second phrase, how you translate it depends on whether they are talking about a) areas within a single district b) areas that belong to different industrial districts, or c) the districts themselves

a) X% of the areas belonging to the industrial district

b) X% of the areas belonging to industrial districts

c) X% of the industrial districts

--------------------------------------------------
Note added at 23 hrs 36 mins (2005-09-29 19:16:54 GMT)
--------------------------------------------------

I agree with Paul that *industrial districts* sounds clumsy; however, this refers to a specific situation that has been extensively described and is widely known in the business and research communities

An example:

Industrial districts and inter-firm co-operation in Italy :

Author(s) Becattini, G., ed, Pyke, F., ed, Sengenberger, W., ed,
Published Geneva : International Institute for Labour Studies, 1990.

Abstract This book focuses on the **industrial districts** of North Central and North Eastern Italy ... It is an aim of the International Institute for Labour Studies to bring to the attention of the public and policy-makers new ideas and developments in the world of industry and labour. The general significance of the **industrial district** phenomenon and its broader implications and value for those concerned with promoting economically efficient, yet socially worthwhile, economic organisations, remains to be seen.




--------------------------------------------------
Note added at 2 days 16 mins (2005-09-30 19:56:54 GMT)
--------------------------------------------------

Check this out
http://www.distretti.org/cgi-db/portale.htm

This map shows what we're talking about http://www.clubdistretti.it/Distretti/mappe/mappadistrettiit...





--------------------------------------------------
Note added at 2 days 1 hr 13 mins (2005-09-30 20:54:01 GMT)
--------------------------------------------------

I hope this clarifies what an *industrial district* is, don't think I can do any better!

http://www.competitiveness.org/article/articleview/14/1/5/

Many terms have been used to describe geographic agglomerations of firms in an industry or related industries. Terms with somewhat different meanings are sometimes used interchangeably, creating confusion and a need for more precise definitions.In particular, it is important to distinguish between:

An industrial cluster (see Porter 1990) is a set of industries related through buyer-supplier and supplier-buyer relationships, or by common technologies, common buyers or distribution channels, or common labor pools.
A regional cluster (see Enright 1992, 1993) is an industrial cluster in which member firms are in close geographic proximity to each other. A more inclusive definition would be: regional clusters are geographic agglomerations of firms in the same or closely related industries
**Industrial districts** (such as the Italian industrial districts described in Brusco 1992; Piore and Sabel 1984; Becattini 1987, 1989; Goodman and Bamford 1990; and Pyke, Becattini, and Sengenberger 1992) are concentrations of firms involved in interdependent production processes, often in the same industry or industry segment, that are embedded in the local community and delimited by daily travel to work distances (Sforzi 1992).
A business network consists of several firms that have ongoing communication and interaction, and might have a certain level of interdependence, but that need not operate in related industries or be geographically concentrated in space (see Staber 1996 and Sydow 1996 for discussions of business networks). (...) Given the extensive literature on **industrial districts**, the distinction between regional clusters and industrial districts (a subset of regional clusters) is worth highlighting. Whereas the focal point of an **industrial district** is often a single industry or even a single industry segment, regional clusters generally involve a range of related industries.

**********************

*industrial parks* are a totally different thing

A parcel of land specifically developed to provide lots for industrial activities.
www.omegarealtors.com/Glossary/default.asp

An area zoned and planned for the purpose of industrial development. Usually located outside the main residential area of a city and normally provided with adequate transportation access, including roads and railroad.
www.yourwebassistant.net/glossary/i3.htm

An industrial park is an area of land set aside for industrial development. Industrial parks are usually located close to transport facilities, especially where more than one transport modality (intermodal) coincides: highways, railroads, airports, and navigable rivers. A more "lightweight" version is the office park, which has offices and light industry, rather than heavy industry.
en.wikipedia.org/wiki/Industrial_park

***********************

Districts:
spontaneous, informal development
large area
same industry

Parks:
planned/zoned (the developer usually rents the lots out to companies)
much smaller
factories/companies may have nothing to do with each other

**************

Whew! I don't think I ever went to such lengths to make my point ;-)