PubMed · 5617299
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I J Bravo. [Demography and development].. https://pubmed.ncbi.nlm.nih.gov/5617299/
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Since the discovery of a power law scaling between the mean and variance of natural populations, this phenomenon has been observed for a variety of species. Here, we show that the same form of power law scaling also occurs in measles case reports in England and Wales. Remarkably this power law holds over four orders of magnitude. We consider how the natural experiment of vaccination affects the slope of the power law. By examining simple generic models, we are able to predict the effects of stochasticity and coupling and we propose a new phenomenon associated with the critical community size.
We specify a set of equations defining a dynamic model of international migration and estimate its parameters by using data specially collected in Mexico. We then used it to project the a hypothetical Mexican community population forward in time. Beginning with a stable population of 10,000 people, we project ahead 50 years under three different assumptions: no international migration; constant probabilities of in- and out-migration, and dynamic schedules of out- and in-migration that change as migratory experience accumulates. This exercise represents an attempt to model the self-feeding character of international migration noted by prior observers and theorists. Our model quantifies the mechanisms of cumulative causation predicted by social capital theory and illustrates the shortcomings of standard projection methodologies. The failure to model dynamically changing migration schedules yields a 5% overstatement of the projected size of the Mexican population after 50 years, an 11% understatement of the total number of U.S. migrants, a 15% understatement of the prevalence of U.S. migratory experience in the Mexican population, and an 85% understatement of the size of the Mexican population living in the United States.
This paper examines medical savings accounts combined with high-deductible catastrophic health plans (MSA/CHPs), exploring the possible consequences of making tax preferred MSA/CHPs available to the entire employment-related health insurance market. The paper uses microsimulation methods to examine the equilibrium effects of MSA/CHPs on health care and non-health care expenditures, tax revenues, insurance premiums, and exposure to risk. If MSA/CHPs are offered alongside comprehensive plans, biased MSA/CHP enrollment can lead to premium spirals that drive out comprehensive coverage. Our estimates also raise concerns about equity, insofar as those who stand to lose the most tend to be poorer and in families with infant children.