Search PubMed⌕ Search

Biomedical subjects

N Keyfitz

Publications and source records attributed to N Keyfitz.

At least 19 recordsLinked to original sources
PubMed1996

Population growth, development and the environment.

When Population Studies was founded in 1946 a main preoccupation of demographers and of the public was the prospective decline of the British population, and the falling off of its quality because on the average a poor family had more children than a better-off one. Over the course of the 50 years interests have shifted to the aging of populations as births decline and mortality improves; immigration, immigrants being welcomed for the decades after the war, and subsequently facing hostile political pressures; environmental degradation and the spread of new diseases. The fall in the birth rate, required both for development and for protection of the environment, is spreading from the original industrialized countries of Europe and America to Asia, somewhat more slowly to Latin America, slowest of all to Africa.

Environment↗
PubMed1994

Influence of human reproduction on environment. What features of biology and economics cause them to see population differently?

Disciplinary isolation: like species with common descent, between whom a barrier has arisen, the disciplines have evolved independently. Each discipline evolves on its own dynamic. We are not concerned with opinions of eccentric individual scholars, but with the mainstreams, in particular of biology and economics that today strongly disagree. The disciplines have changed sides. Biology and economics disagreed also in the 19th century, but then biologists were optimists, economists pessimists, on the population-holding capacity of the Earth. Words are used differently in different disciplines, and that arises from and maintains different styles of thought, so that language is one of the barriers between disciplines. A serious matter when "data do not support family planning" is taken as an argument against family planning. Failure to support the hypothesis being tested by no means proves the hypothesis; it is as likely to show merely that the data are inadequate.

Biology↗
PubMed1993

Are there ecological limits to population?

Policy on population and environment in the United States and abroad has been vacillating, unsure of its course; it would be more decisive if the several disciplines could agree on the nature of the problems and their urgency. The two disciplines principally concerned are biology and economics, and the contribution of this paper is to identify eight of the many axes or directions on which the methods and traditions of the two are different. For example, the first of the axes runs between contingency and orderly progress, with biology tending to seek out the former and economics the latter; thus biologists can more easily comprehend catastrophes, such as the demise of the dinosaurs or widespread desertification. The third axis concerns indefinite market-driven substitutability, seen by economists as resulting from scientific discovery; natural scientists, including biologists, whose discoveries make possible the substitutions, are skeptical. Axis 7 results from the fact that economics concentrates on goods that are on the market, and so deals with a truncated part of the commodity cycle, while ecology aims at the whole; because goods disappear from economic statistics once they pass into the hands of consumers many of their ecological effects are invisible. I believe that from similar further study of the two disciplines a common set of policy recommendations will ultimately emerge.

Ecology↗
PubMed1992

The political context of immigration: Europe and America.

The author examines and compares the immigration acculturation philosophies of Europe and the United States. He finds that "present [discrimination] problems throughout Europe show the enormous difficulty of accepting foreigners for countries whose nationhood depends on the ideal common ancestry. The United States on the whole has been heterogeneous almost from the start, and has had unprecedented success in making a community out of culturally heterogeneous elements." Recommendations for future research are included.

Acculturation↗
PubMed1991

Population and development within the ecosphere: one view of the literature.

"Contemporary academic economists, unlike those of the nineteenth century, find that although population growth and density can have bad effects on development, these will only be severe with wrong economic policies. Technical advance and substitution in free markets avoid major difficulties, for example shortage of materials. But ecologists see the poor cutting trees for firewood, the rich pouring carbon in to the atmosphere, and doubt the capacity of the environment to absorb the effects of dense and growing populations and their present technologies. On both sides are distinguished scholars, whose writings cannot here be covered exhaustively, but only enough said for background to the question posed to demographers: Should this central population issue not be on our research agendas?"

Conservation of Natural Resources↗
PubMed1990

The profile of intercohort increase.

"The paper develops a technique for identifying the cohorts that initiated what in the 1950s was designated the population explosion. A numerical example is given for Indonesia, but essentially the same picture appears for many other countries, and for the aggregate of the world. The intercohort increase can be estimated for each age using two successive censuses; the method here developed gives very nearly the same increase whatever age is used for the estimate." (SUMMARY IN FRE)

Asia↗
PubMed1988

A Markov chain for calculating the durability of marriage.

"The usual Markov model of marriage permits informative experiments on the effect of alterations in the transition rules. It can tell, for example, what difference it would make to the durability of marriage if there was no divorce and the other transitions were as observed. This is in addition to the capacity of the usual model to find the effect of small changes in the transition rates. Canadian data for 1970-1982 permit comparisons over time, and show among other things not only that married men live longer than single, but that the difference is increasing; the increase in the 'marriage bonus' over time also appears for women." (SUMMARY IN FRE)

Americas↗
PubMed1985

The demographics of unfunded pensions.

The performance of pay-as-you-go old-age insurance under different demographic conditions can be estimated from a metric consisting of the implicit rate of return to successive cohorts. The author shows a positive return for the prospective population over the next few years, but for cohorts born after the end of the century returns will become sharply negative. A decline in returns is typical of pay-as-you-go schemes as they mature, and a change to negative returns is typical in particular as the birth rate falls under fixed economic conditions. The return can be kept positive by greatly increased fertility or immigration. Taking labor-force participation rates into account, and supposing entitlement independent of contribution, gives much larger negative rates of return, however. The main calculations considered here are for schemes with a constant pension. If the contribution rather than the pension is kept constant then the disparities between cohorts with respect to their returns are smaller, and although the negative returns for future generations then set in earlier they are smaller. The conclusions of the paper are broadly applicable to any population that showed a baby boom after World War II and replacement-level or lower fertility subsequently.

Americas↗
PubMed1984

[A demographic analysis of multiple contingencies].

Using the multidimensional model developed by Andrei Rogers, the authors formulate a method for analyzing the interaction between and the multiplicity of certain behavior patterns such as migration. "The present article attempts to present a conceptual approach which extends classical demographic analysis to multiple phenomena or which adapts the analysis of mobility to demographic methods." (summary in ENG, SPA)

Behavior↗