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The Impact of Residential Mobility on Measurements of Neighbourhood Effects. Lina Bergström Institute for Housing and Urban Studies Uppsala University lina.bergstrom@ibf.uu.se.
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The Impact of Residential Mobility on Measurements of Neighbourhood Effects Lina Bergström Institute for Housing and Urban Studies Uppsala University lina.bergstrom@ibf.uu.se
Source: Andersson, R (2008) Neighbourhood Effects and the Welfare State. Towards a European research agenda? Schmollers Jahrbuch 128 pp. 1-14 (Data from GeoSweden)
Change in Ethnic Composition 1991-2006, Tensta, Stockholm Source: GeoSweden
A holistic framework Moving patterns Moving patterns Moving patterns Individual mobility Time t Time t+1 Neighbourhood conditions Neighbourhood conditions Aggregate behaviour Individual behaviour Aggregate behaviour Individual behaviour
Challenge 1: Exposure time • Transmission mechanisms require a critical amount of exposure Problems: • How long residing in neighbourhood? - is exposure sufficient? - affects on impact • During what time in life? • How do exposure to different neighbourhoods relate to each other?
Challenge 2: Neighbourhood Change • Neighbourhood context may change over time • The urban opportunity structure may change over time Problems: • Estimate exposure to constant neighbourhood? • Observable and unobservable characteristics • Aggregate levels vs. individual influence
Solutions: • Sampling • Exposure to neighbourhood Problem: changing contexts • Exposure to environmental characteristic Problem: impact of specific neighbourhoods • Exposure to stable neighbourhood context Problem: small, unrepresentative and biased samples • Control variables for exposure time and changing contexts Problem: finding enough and “right” control variables • Complementary data, e.g. surveys
Challenge 3: Selection bias • People select themselves into neighbourhoods for reasons unknown to the researcher • Reasons might be correlated with outcome • Most scholars agree that bias exist, some argue that all effects are due to bias Problem: Eliminating selection bias to find effect of neighbourhood
Solutions: • Experimental data (like MTO) Problem: Rare, must fulfil criteria of exposure and selection bias control • Statistical techniques • Sibling analysis • Difference modelling • Instrumental variables Problem: Eliminate bias but says nothing about selection processes • Modelling neighbourhood choice Problem: Explanatory value need to be good for eliminating selection bias
Challenge 4: Endogeneity bias • The choice of neighbourhood as a joint decision with choice of tenure, type of housing, length of stay • All may be correlated with outcome Problem • Isolating the effect of the neighbourhood Solution • Instrumental variables Problem: finding good instruments
Conclusion: Implications for research • Residential mobility and neighbourhood effects are two interconnected fields • Mobility must be incorporated into models • Longitudinal data! • Control for exposure (ind./neigh’d) • Control for selection bias • Control for endogeneity • Or: Results will be biased or do not (necessarily) estimate neighbourhood effects!