BackgroundThe concurrency hypothesis asserts that high prevalence of overlapping sexual partnerships explains extraordinarily high HIV levels in sub-Saharan Africa. Earlier simulation models show that the network effect of concurrency can increase HIV incidence, but those models do not account for the coital dilution effect (non-primary partnerships have lower coital frequency than primary partnerships).MethodsWe modify the model of Eaton et al (AIDS and Behavior, September 2010) to incorporate coital dilution by assigning lower coital frequencies to non-primary partnerships. We parameterize coital dilution based on the empirical work of Morris et al (PLoS ONE, December 2010) and others. Following Eaton et al, we simulate the daily transmission of HIV over 250 years for 10 levels of concurrency.ResultsAt every level of concurrency, our focal coital-dilution simulation produces epidemic extinction. Our sensitivity analysis shows that this result is quite robust; even modestly lower coital frequencies in non-primary partnerships lead to epidemic extinction.ConclusionsIn order to contribute usefully to the investigation of HIV prevalence, simulation models of concurrent partnering and HIV epidemics must incorporate realistic degrees of coital dilution. Doing so dramatically reduces the role that concurrency can play in accelerating the spread of HIV and suggests that concurrency cannot be an important driver of HIV epidemics in sub-Saharan Africa. Alternative explanations for HIV epidemics in sub-Saharan Africa are needed.

Empirical studies of agrarian production in developing countries often find that small farms possess a productivity advantage over larger farms. Eswaran and Kotwal (1986) famously derive this inverse farm‐size/productivity relationship from the structure of agrarian production. The focal prediction of their model is that, in otherwise equivalent economies, a more egalitarian land distribution raises both output and producer welfare. The traditional (spot) procurement system implicit in the Eswaran and Kotwal model, however, diverges fundamentally from modern (contractual) procurement practices. We therefore develop a new model of agrarian production in order to determine whether the introduction of a modern value chain alters the welfare effects of land redistribution. The inverse farm‐size/productivity relationship persists in our model, but we find that more egalitarian land distribution leads to nonmonotonic changes in producer welfare. We also find that the introduction of a modern sector can harm the laboring classes.

Labor turnover, job mobility, wage record data,

We present a neo‐Kaleckian growth model with both consumer and corporate debt. The model's macrodynamic and stability characteristics differ from singleߚdebt models, yet some steadyߚstate results persist. For example, a surge in ‘animal spirits’ is good for steadyߚstate growth, and consumer borrowing can help to sustain aggregate demand. Stable steady states are characterized by a kind of ‘euthanasia of the rentier’. Consumer credit conditions influence effective demand, the profit rate and economic growth. Looser consumer credit conditions have a steadyߚstate growth effect and can enhance system stability. In this restricted sense, looser consumer credit conditions are good for macroeconomic stability.