In theory, a self-contained labour market area is one in which all commuting occurs within the boundary of the area. In practice, there are entirely separate labour market areas. For those involved in labour market analysis and planning, it is useful to be able to define zones in which the bulk of the resident population also work, so, by applying a multi-stage allocation process, the UK Office for National Statistics has defined ‘Travel to Work Areas’ as approximations of self-contained labour markets. The basic criteria used for defining a TTWA are that, of the resident economically active population,

• • at least 75% actually work in the area,

• • of everyone working in the area, at least 75% actually live in the area.

The definitive minimum working population in a TTWA is 3 500, but many are much larger—indeed, the whole of London and surrounding area forms one TTWA.

For the methodology, see appendix 1, Office for National Statistics 1991 Travel-to-Work Areas, and for an update, see M. Coombes, S. Raybould, and C. Wymer (2005).

http://www.ons.gov.uk/ons/guide-method/geography/beginner-s-guide/other/travel-to-work-areas/index.html Office for National Statistics 1991-based Travel to Work Areas.

http://www.ons.gov.uk/ons/taxonomy/index.html?nscl=Travel+to+Work+Area National Statistics, Travel to Work Areas.