Data from household surveys have increasingly been used as a basis for social policy. They are generally inappropriate for obtaining information about the poorest, and therefore for policies concerned with tackling poverty and deprivation. They omit certain groups by design: the homeless; those in institutions; and mobile, nomadic or pastoralist populations. In addition, in practice, they typically under-represent those in fragile, disjointed or multiple occupancy households, those in urban slums and those in areas deemed as insecure. These sub-groups constitute a pretty comprehensive, ostensive definition of the ‘poorest’.
The sources of worldwide estimates of the missing populations are briefly described, with those for the UK discussed in greater detail, paying attention to their likely income and wealth. At least 250 million of the poorest of the poor are omitted worldwide; and in the UK about half a million of the poorest are missing from survey sample frames.
In the UK, these ‘missing’ population sub-groups bias the analysis of income inequalities and affect the validity of formulae that have been developed for the geographical allocation of resources to health and social care.