Data Sources and Issues in Measurement
This chapter details the data sources deployed and the approaches to deriving measures from them. National definitions of urban settlements vary but are demonstrated to match satellite imagery surprisingly well. Most selected sources ask if the place of origin was rural or urban, though in several censuses this is imputed on the nature of the location of origin, rejecting instances where locations prove too diverse; significant contrasts are not found between the two approaches. Those sources that ask place of birth show significantly lower lifetime migration from urban to rural areas than those reporting only location during childhood; their rural-urban migration propensities do not differ. Measures of migrant flow rates, return migration, and other temporary moves require interim location information. Sources reporting the previous location and duration of residence prove more useful than those asking location five years before. A contention of symmetry between rural-urban and urban-rural migration propensities is rejected.