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(2005) Measurement: Interdisciplinary Research and Perspectives, 3, 236-237.

Are the World's Poor Qualitatively Distinct From the Fortunate Few?

G. Scott Acton
Rochester Institute of Technology

Iceland's target article provides much food for thought on the distinction between poverty and wealth, but one unexamined assumption warrants comment: that, properly defined, a poverty line exists. This commentary challenges that assumption on methodological grounds that invite empirical testing rather than further definitional refinement. It is argued that the basic problem is not absolute versus relative but categorical versus dimensional. Wealth and poverty may not be qualitatively distinct categories but may lie on a continuum--this hypothesis can and should be tested.

Let us assume that investigators are able to identify a group of persons who are impoverished and another group who are not. The identification can be on the basis of expert consensus or a systematic algorithm. Let us also assume that investigators are able to identify indicators relevant to this distinction, such as the following basic human rights: food, clean water, shelter, healthcare, education. Then let us see whether the poor are qualitatively distinct from the wealthy (e.g., those who do not have to worry about whether they will eat tomorrow) on these indicators on the basis of differential item functioning or lack of factorial invariance (cf. De Boeck, Wilson, & Acton, 2005). To be merely quantitatively distinct, the poor would be lower than the rich on all the basic human rights to the same degree, but to be qualitatively distinct, the human rights would mean something completely different among the poor than among the rich. For example, electricity may mean something different in poor countries than in rich ones; electricity may be so rare in third-world counties that it is lacking even among community leaders, whereas in industrialized countries electricity may light the streets where the homeless live.

We can also compare distributions of persons within a particular group, such as the impoverished, with respect to within-group heterogeneity as measured by Cronbach's alpha. This distinction, although important conceptually, may be less important in practice, because it seems evident that within the category of poverty people differ on the indicators. For example, one particular subset of the poor, such as those in many third-world countries, may live in abject misery, whereas another group's deprivation can only be recognized by way of comparison with the wealthy. Such heterogeneity would become important, however, if it were of a qualitative kind, in which case subtypes with different profiles of poverty should be considered. Such within-group heterogeneity, which could be revealed by latent profile analysis or a mixture model with different mean and covariance structures depending on the mixture component, could have implications for the manner in which interventions should be deployed. Specifically, the most sensible intervention would be to provide preferentially for the poor who are worst off.

For example, treatment resistant tuberculosis has emerged as a serious problem in some third-world countries. These poor people differ from other poor people in carrying a highly lethal infectious disease which, if left untreated, could become an epidemic (Farmer, 2003). The treatment for treatment resistant tuberculosis involves bypassing traditional drugs in favor of a more expensive regimen. Such expense is justified on grounds of basic human rights, but it also happens that treatment resistant tuberculosis promises to proliferate beyond the third world and threaten the rich as well. Thus, infectious disease is very "democratic" in its effects, encouraging us to reduce the difference in healthcare between rich and poor and make effective treatments available to all.


De Boeck, P., Wilson, M., & Acton, G. S. (2005). A conceptual and psychometric framework for distinguishing categories and dimensions. Psychological Review, 112, 129-158.

Farmer, P. (2003). Pathologies of power: Health, human rights, and the new war on the poor. Berkeley, CA: University of California Press.

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