PubMed Health⌕ Search

Biomedical subjects

W B Arthur

Publications and source records attributed to W B Arthur.

8 recordsLinked to original sources
PubMed1984

The analysis of linkages in demographic theory.

Many seemingly different questions that arise in the analysis of population change can be phrased as the same technical question: How, within a given demographic model, would variable y change if the age- or time-specific function f were to change arbitrarily in shape and intensity? At present demography lacks the machinery to answer this question in analytical and general form. This paper suggests a method based on modern functional calculus for deriving closed-form expressions for the sensitivity of demographic variables to changes in input functions or schedules. It uses this "linkage method" to obtain closed-form expressions for the response of the intrinsic growth rate, birth rate, and age composition of a stable population to arbitrary marginal changes in its age patterns of fertility and mortality. It uses it also to obtain expressions for the transient response of the age composition of a nonstable population to time-varying changes in the birth sequence, and to age-specific fertility and mortality patterns that change over time. The problem of "bias" in period vital rates is also looked at.

Adult↗
PubMed1982

Immigration and the stable population model.

This paper reports on work aimed at extending stable population theory to include immigration. its central findings is that, as long as fertility is below replacement, a constant number and age distribution of immigrants (with fixed fertility and mortality schedules) lead to a stationary population. Neither the level of the net reproduction rate nor the size of the annual immigration affects this conclusion; a stationary population eventually emerges. How this stationary population is created is studied, as is the generational distribution of the constant annual stream of births and of the total population. It is also shown that immigrants and their early descendants may have fertility well above replacement (as long as later generations adopt and maintain fertility below replacement), and the outcome will still be a long-run stationary population.

Adolescent↗
PubMed1982

The ergodic theorems of demography: a simple proof.

Standard proofs of the ergodic theorems of demography rely on theorems borrowed from positive matrix theory, tauberian theory, and the theory of time-inhomogeneous Markov matrices. These proofs are efficient and expedient, but they give little direct insight into the mechanism that causes ergodicity. This paper proposes a simple and unified proof of the two ergodic theorems. It is shown that the birth dynamics can be decomposed into a smoothing process that progressively levels out past fluctuations in the birth sequence and a reshaping process that accounts for current period-to-period changes in vital rates. The smoothing process, which causes the birth sequence to lose information on its past shape, is shown to be the ergodic mechanism behind both theorems.

Birth Rate↗
PubMedDate not supplied

Increasing returns and the new world of business.

Our understanding of how markets and businesses operate was passed down to us more than a century ago by English economist Alfred Marshall. It is based on the assumption of diminishing returns: products or companies that get ahead in a market eventually run into limitations so that a predictable equilibrium of prices and market shares is reached. The theory was valid for the bulk-processing, smokestack economy of Marshall's day. But in this century, Western economies have gone from processing resources to processing information, from the application of raw energy to the application of ideas. The mechanisms that determine economic behavior have also shifted--from diminishing returns to increasing returns. Increasing returns are the tendency for that which is ahead to get further ahead and for that which is losing advantage to lose further advantage. If a product gets ahead, increasing returns can magnify the advantage, and the product can go on to lock in the market. Mechanisms of increasing returns exist alongside those of diminishing returns in all industries. But, in general, diminishing returns hold sway in the traditional, resource-processing industries. Increasing returns reign in the newer, knowledge-based industries. Modern economies have split into two interrelated worlds of business corresponding to the two types of returns. The two worlds have different economics. They differ in behavior, style, and culture. They call for different management techniques, strategies, and codes of government regulation. The author illuminates those differences by explaining how increasing returns operate in high tech and in service industries. He also offers advice to managers in knowledge-based markets.

Commerce↗