Delineating sub city districts for decision making An attempt to automate the process

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Delineating sub city districts for decision
makingAn attempt to automate the process
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Context

• Urban policies are heavily territory based
• 751 Zones urbaines sensibles (ZUS)
• Need for an evaluation
• Zones in use where defined in 1996-1997
• Town planning has modified the structure of
  several urban areas
• Urban riots of end of 2005 needed a political
  response (within suburbs, millions are set on
  fire too)
• Need for extensions
• New zones are already in use locally (800)
• Formalized additions already exist for specific
  purposes

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Question (December 2005)

• For the national level (urban affairs ministry)
• Target cities and zones absolutely needing
  attention
• Give a filter to set priorities among locally
  defined zones
• For the local level (regional government and
  cities)
• Provide data to quantify problems in selected
  zones
• Provide methodological help to find or to argue
  for new zones

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Challenge no 1Find a relevant basic block

• Standard geographical units are not relevant
• Block size around 2 000 inhabitants, existing
  zones ranges from 500 to 50 000, target for new
  one has only a (theoretical) lower bound of 2
  000.
• Design essentially based on form of the built up
  area, not suitable for measuring anything else
• gt Design zones without using existing zoned data

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The trap with standard geographical blocksfrom a
classroom example
Standard zones for dissemination
1000 inhabitants Unemployment 10
1000 inhabitants Unemployment 10
Unobservable zones
1000 inhabitants Unemployment 20
1000 inhabitants Unemployment 20
Deprived neighbourhood
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to real cases Unemployment in City of
Gennevilliers,
Available on the web,using standard
dissemination blocks
From individual data,using spatial analysis
tools
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Not only a problem when drawing mapsUrban
segregation ranking among large citiesaccording
to Duncan and Duncan index(Low/high
qualification households)
Basic geographical block size (standard
dissemination blocks)
2 000 inhabitants
5 000 inhabitants
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Challenge no 2Find relevant sources

• Recent, available at detailed geographical level
  within a short timing?
• Census ok but too old (1999)
• Administrative sources, recent but
• Disconnected themes income, unemployment,
  employment
• Biased no disposable income, no LFS
  unemployment, etc
• Covering large but not complete and different
  fractions of the population
• gt Each one must be used separately
• Geography partially processed
• gt To be finished with estimations of individual
  location
• gt Use rounded coordinates grided data (100m x
  100m)
• gt Prefer biased recent data to old but correct
  data
• Not THE answer but a set of disconnected answers

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The proposal a set of mapsshowing the rough
outlines of the zones having a high proportion
of deprived population, relatively to local
situation
Blue the zones currently in use (ZUS) Red
suggested areas where to design new zones Grey
spatial distribution of the global population
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Challenge no 3Human factors

• Inside the INSEE two revolutions
• Whole environment is different new data, new
  tools
• gttargeted training,
• Implies active involvement in a decisional
  process
• Outside finish the work!
• The proposal from INSEE is only a set of hints
  for knowing where to create a new zone, not its
  outline
• Other (non quantitative) data must be used
  local mood
• Priority ranking has to be done

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From data to final map
1) Simplify the maps
Rough grid data to smoothed data
4)Superpose the maps
3) Extract the outlines
2) Combine the maps
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Simplifying the viewsNonparametric density
estimation
Longitudinal section, 100m step.
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Selecting the areasRelative thresholds
Selected areas
Ratio
Value of the threshold select the upper half
of inhabited zones more deprived than the whole
city average
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It works!Same data source, several cities(low
qualifications from wage payment registers)
Rennes
Rouen
North of Paris
Roubaix
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The need for several points of viewSame city,
several data sources La Rochelle
Administrative artefact
Low income from social family benefits
Low income from income tax registers
Already known as a potential zone
New zone
Low qualifications from unemployment registers
Low income from health insurance registers
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That is not science fiction!

• At national level
• One full set of maps was disseminated in the web
  site of the urban affairs ministry (mid 2006)
• Thresholds were used as a segregation index to
  set priorities among cities
• Dissemination of such maps within insee.fr is
  planned for 2008
• At regional level
• Collaborative work initiated between regional
  statisticians and many cities
• Turned to be a more general analysis tool still
  in use
• Grided data production is no more an exception

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Thank youQuestions?