February 15, 2008 Seminar

Expectations, Networks and Interventions: Research on HIV/AIDS in Malawi

Hans-Peter Kohler, University of Pennsylvania

Abstract: The talk will present three areas of recent research conducted as part of the Malawi Diffusion and Ideational Change Project. The first part discusses present a newly-developed interactive elicitation methodology to collect probabilistic expectations in a developing country context with low levels of literacy and numeracy, and we evaluate the feasibility and success of this method for a wide range of outcomes in rural Malawi. We find that respondent's answers about subjective expectations respect basic properties of probabilities, and vary meaningfully with observable characteristics and past experience. From a substantive point of view, the elicited expectations indicate that individuals are generally aware of differential risks. While many expectations---including also the probability of being currently infected with HIV---are well-calibrated compared to actual probabilities, mortality expectations are substantially over-estimated compared to lifetable estimates. This overestimation may lead individuals to underestimate the benefits of adopting HIV risk-reduction strategies. The second part of the talk focuses on a recent sociocentric study of sexual network on Likoma Island (Lake Malawi) that aims at investigating the structure and characteristics of sexual networks among the general population. The study documents the existence of a large and robust sexual network linking a substantial fraction of the island's young adult population: half of all sexually active respondents were connected in a giant network component, and more than a quarter were linked through multiple independent chains of sexual relationships. This high network connectivity emerges within short time frames. The prevalence of HIV also varied significantly across the network, with sparser regions having a higher HIV prevalence than densely connected components. Several risk factors related to sexual mixing patterns help explain differentials in HIV prevalence across network locations. Contrary to claims that sexual networks in rural sub-Saharan Africa are too sparse to sustain generalized HIV epidemics, therefore, the structure of the networks observed in Likoma appears compatible with a broad diffusion of HIV among lower-risk groups. The non-homogeneous distribution of HIV infection within the network suggests that network characteristics are an important determinant of the dynamics of HIV spread within a population. The third part of the talk presents some preliminary analyses of a randomized intervention studying the consequences for learning one's HIV status for subsequent behaviors.

Papers by Hans-Peter Kohler: