Two Models for Multiregional Population Dynamics

1973 ◽  
Vol 5 (1) ◽  
pp. 31-43 ◽  
Author(s):  
G Feeney
Keyword(s):  
United States ◽  
Population Dynamics ◽  
General Model ◽  
Nonlinear Models ◽  
The United States ◽  
Demographic Model ◽  
Interregional Migration ◽  
New Model ◽  
Migration Rates ◽  
Linear And Nonlinear

A general linear demographic model is derived which subsumes a wide variety of previously proposed population models. The general model includes in particular the linear model of interregional population growth and distribution developed by Rogers and others. One feature of this model is criticized, the allocation of outmigrants from any region in constant proportions among possible destination regions. Insofar as persons migrate to economic opportunities, outmigrants will distribute themselves among regions in proportion to these opportunities. Insofar as the economy of a region services its population, opportunities will vary directly with population. This suggests the introduction of a new model which allows for the variable allocation of outmigrants from each region according to the distribution of population among possible destination regions. Such a model is proposed, and it turns out to be nonlinear. The linear and nonlinear models are compared by applying them to the analysis of migration between three regions of the United States during 1955–1960. In the course of developing the new model, a set of interregional migration statistics is defined which eliminates the imperfect duality between interregional in- and out-migration rates.

scholarly journals Asymmetric dynamics between uncertainty and unemployment flows in the United States

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Ali Ahmed ◽  
Mark Granberg ◽  
Victor Troster ◽  
Gazi Salah Uddin
Keyword(s):  
United States ◽  
Business Cycle ◽  
Negative Impact ◽  
The United States ◽  
Large Uncertainty ◽  
Monthly Data ◽  
Uncertainty Measures ◽  
Linear And Nonlinear ◽  
The Business Cycle ◽  
The U.S

AbstractThis paper examines how different uncertainty measures affect the unemployment level, inflow, and outflow in the U.S. across all states of the business cycle. We employ linear and nonlinear causality-in-quantile tests to capture a complete picture of the effect of uncertainty on U.S. unemployment. To verify whether there are any common effects across different uncertainty measures, we use monthly data on four uncertainty measures and on U.S. unemployment from January 1997 to August 2018. Our results corroborate the general predictions from a search and matching framework of how uncertainty affects unemployment and its flows. Fluctuations in uncertainty generate increases (upper-quantile changes) in the unemployment level and in the inflow. Conversely, shocks to uncertainty have a negative impact on U.S. unemployment outflow. Therefore, the effect of uncertainty is asymmetric depending on the states (quantiles) of U.S. unemployment and on the adopted unemployment measure. Our findings suggest state-contingent policies to stabilize the unemployment level when large uncertainty shocks occur.

Diaspora in the United States: Chinese and Indians Compared

2010 ◽  
Vol 6 (2) ◽  
pp. 286-310 ◽  
Author(s):  
Emily Skop ◽  
Wei Li
Keyword(s):  
United States ◽  
Racial Discrimination ◽  
20Th Century ◽  
The United States ◽  
Foreign Born ◽  
Migration Rates ◽  
China And India ◽  
History Of ◽  
Migrant Groups ◽  
The U.S

AbstractIn recent years, the migration rates from both China and India to the U.S. have accelerated. Since 2000 more than a third of foreign-born Chinese and 40% of foreign-born Indians have arrived in that country. This paper will document the evolving patterns of immigration from China and India to the U.S. by tracing the history of immigration and racial discrimination, the dramatic transitions that have occurred since the mid-20th century, and the current demographic and socioeconomic profiles of these two migrant groups.

scholarly journals How Quickly are Road-killed Snakes Scavenged? Implications for Underestimates of Road Mortality

2011 ◽  
Vol 127 (2) ◽  
pp. 184-188 ◽  
Author(s):  
BRETT A. DEGREGORIO ◽  
THOMAS E. HANCOCK ◽  
DAVID J. KURZ ◽  
SAM YUE
Keyword(s):  
United States ◽  
Population Dynamics ◽  
Community Composition ◽  
The United States ◽  
The Other ◽  
Road Mortality ◽  
Correction Factors ◽  
Significant Extent ◽  
Removal Time ◽  
Maritime Forest

Abstract Annually, millions of snakes are killed on roads in the United States. Because of their potential abundance and ease of collection, many researchers have used road-killed snakes to examine community composition, movement patterns, and population dynamics. However, few previous studies have accounted for snake carcasses that are removed from roads by scavengers. Snake carcasses were placed at randomly selected locations along 2 km of road, one traversing maritime forest and the other surrounded by dune habitat. Carcasses in forested habitat were removed more often (100% vs 40%) and more quickly (8 hr vs 11 hr) than those placed in dune habitat. Half of the carcasses (50%) were removed within eight hours of placement and all carcasses were removed at night. Species and size of carcasses did not affect removal time. Removal time and scavenging intensity of snake carcasses most likely varies across regions and habitats. Furthermore, because scavenging appears to occur quickly and to such a significant extent, it may confound results of studies examining patterns of road-mortality. Thus, investigators that use data from road-killed snakes would benefit from a concurrent investigation of scavenging and application of appropriate correction factors to avoid underestimation of snake mortality.

scholarly journals Introductory Models of COVID-19 in the United States

2021 ◽  
Vol 2 (3) ◽  
pp. 74-98
Author(s):  
Peter Hugo Nelson
Keyword(s):  
United States ◽  
The United States ◽  
Transition Function ◽  
Model Parameters ◽  
Microsoft Excel ◽  
New Model ◽  
Social Distancing ◽  
Unlimited Growth ◽  
Least Squares Techniques

ABSTRACT Students develop and test simple kinetic models of the spread of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. Microsoft Excel is used as the modeling platform because it is nonthreatening to students and it is widely available. Students develop finite difference models and implement them in the cells of preformatted spreadsheets following a guided inquiry pedagogy that introduces new model parameters in a scaffolded step-by-step manner. That approach allows students to investigate the implications of new model parameters in a systematic way. Students fit the resulting models to reported cases per day data for the United States using least squares techniques with Excel's Solver. Using their own spreadsheets, students discover for themselves that the initial exponential growth of COVID-19 can be explained by a simplified unlimited growth model and by the susceptible-infected-recovered (SIR) model. They also discover that the effects of social distancing can be modeled using a Gaussian transition function for the infection rate coefficient and that the summer surge was caused by prematurely relaxing social distancing and then reimposing stricter social distancing. Students then model the effect of vaccinations and validate the resulting susceptible-infected-recovered-vaccinated (SIRV) model by showing that it successfully predicts the reported cases per day data from Thanksgiving through the holiday period up to 14 February 2021. The same SIRV model is then extended and successfully fits the fourth peak up to 1 June 2021, caused by further relaxation of social distancing measures. Finally, students extend the model up to the present day (27 August 2021) and successfully account for the appearance of the delta variant of the SARS-CoV-2 virus. The fitted model also predicts that the delta variant peak will be comparatively short, and the cases per day data should begin to fall off in early September 2021, counter to current expectations. This case study makes an excellent capstone experience for students interested in scientific modeling.

Population dynamics of muskrats and mink: investigating contemporary patterns in a classic predator-prey system

2021 ◽  
Author(s):  
Adam A Ahlers ◽  
Timothy P Lyons ◽  
Edward J Heske
Keyword(s):  
United States ◽  
Population Dynamics ◽  
Density Dependence ◽  
American Mink ◽  
Population Cycles ◽  
The United States ◽  
Parameter Estimates ◽  
Predator Prey ◽  
Cycle Lengths ◽  
Southern Half

A well-studied predator-prey relationship between American mink (Neovison vison (Schreber, 1777)) and muskrats (Ondatra zibethicus (Linnaeus, 1766)) in Canada has advanced our understanding of population cycles including the influence of density dependence and lagged responses of predators to prey abundances. However, it is unclear if patterns observed in Canada extend across the southern half of their native range. We used data from the United States to create a 41-year time series of mink and muskrat harvest reports (1970-2011) for 36 states. After controlling for pelt-price effects, we used 2nd order autoregressive and Lomb-Scargle spectral density models to identify the presence and periodicity of muskrat population cycles. Additionally, we tested for evidence of delayed or direct density dependence and for predator-driven population dynamics. Our results suggest muskrat populations may cycle in parts of the United States; however, results varied by modeling approaches with Lomb-Scargle analyses providing more precise parameter estimates. Observed cycle lengths were longer than expected with weak amplitudes and we urge caution when interpreting these results. We did not detect evidence of a predator-prey relationship driven by a lagged numerical response of American mink. American mink and muskrat fur returns were largely correlated across the region suggesting extraneous factors likely synchronize both populations.

How Modern is Modern Marketing? Marketing's Evolution and the Myth of the “Production Era”

1988 ◽  
Vol 52 (1) ◽  
pp. 108-125 ◽  
Author(s):  
Ronald A. Fullerton
Keyword(s):  
United States ◽  
The United States ◽  
Marketing Practice ◽  
New Model

The widely accepted belief in a Production Era implies that serious and sophisticated marketing is a recent phenomenon. Analyzing conditions in Britain, Germany, and the United States, the author shows that the Production Era concept obscures the extent and level of development of earlier marketing practice, as do the Sales Era and Marketing Era concepts. A new model of marketing's evolution is used to propose a more accurate periodization of modern marketing's development.

scholarly journals Introduction, Evolution, and Dissemination of Influenza A Viruses in Exhibition Swine in the United States during 2009 to 2013

2016 ◽  
Vol 90 (23) ◽  
pp. 10963-10971 ◽  
Author(s):  
Martha I. Nelson ◽  
Karla M. Stucker ◽  
Seth A. Schobel ◽  
Nídia S. Trovão ◽  
Suman R. Das ◽  
...  
Keyword(s):  
United States ◽  
Population Dynamics ◽  
Influenza A Virus ◽  
Influenza A ◽  
The United States ◽  
Viral Population ◽  
Influenza A Viruses ◽  
Swine Industry ◽  
Virus Diversity ◽  
Agricultural Fairs

ABSTRACT The swine-human interface created at agricultural fairs, along with the generation of and maintenance of influenza A virus diversity in exhibition swine, presents an ongoing threat to public health. Nucleotide sequences of influenza A virus isolates collected from exhibition swine in Ohio ( n = 262) and Indiana ( n = 103) during 2009 to 2013 were used to investigate viral evolution and movement within this niche sector of the swine industry. Phylogenetic and Bayesian analyses were employed to identify introductions of influenza A virus to exhibition swine and study viral population dynamics. In 2013 alone, we identified 10 independent introductions of influenza A virus into Ohio and/or Indiana exhibition swine. Frequently, viruses from the same introduction were identified at multiple fairs within the region, providing evidence of rapid and widespread viral movement within the exhibition swine populations of the two states. While pigs moving from fair to fair to fair is possible in some locations, the concurrent detection of nearly identical strains at several fairs indicates that a common viral source was more likely. Importantly, we detected an association between the high number of human variant H3N2 (H3N2v) virus infections in 2012 and the widespread circulation of influenza A viruses of the same genotype in exhibition swine in Ohio fairs sampled that year. The extent of viral diversity observed in exhibition swine and the rapidity with which it disseminated across long distances indicate that novel strains of influenza A virus will continue to emerge and spread within exhibition swine populations, presenting an ongoing threat to humans. IMPORTANCE Understanding the underlying population dynamics of influenza A viruses in commercial and exhibition swine is central to assessing the risk for human infections with variant viruses, including H3N2v. We used viral genomic sequences from isolates collected from exhibition swine during 2009 to 2013 to understand how the peak of H3N2v cases in 2012 relates to long-term trends in the population dynamics of pandemic viruses recently introduced into commercial and exhibition swine in the United States. The results of our spatial analysis underscore the key role of rapid viral dispersal in spreading multiple genetic lineages throughout a multistate network of agricultural fairs, providing opportunities for divergent lineages to coinfect, reassort, and generate new viral genotypes. The higher genetic diversity of genotypes cocirculating in exhibition swine since 2013 could facilitate the evolution of new reassortants, potentially with even greater ability to cause severe infections in humans or cause human-to-human transmission, highlighting the need for continued vigilance.

scholarly journals Population dynamics of cocirculating swine influenza A viruses in the United States from 2009 to 2012

2013 ◽  
Vol 7 ◽  
pp. 42-51 ◽  
Author(s):  
Tavis K. Anderson ◽  
Martha I. Nelson ◽  
Pravina Kitikoon ◽  
Sabrina L. Swenson ◽  
John A. Korslund ◽  
...  
Keyword(s):  
United States ◽  
Population Dynamics ◽  
Influenza A ◽  
Swine Influenza ◽  
The United States ◽  
Influenza A Viruses

scholarly journals Learning from Null Effects: A Bottom-Up Approach

2020 ◽  
Author(s):  
Ala' Alrababa'h ◽  
Scott Williamson ◽  
Andrea Dillon ◽  
Jens Hainmueller ◽  
Dominik Hangartner ◽  
...  
Keyword(s):  
United States ◽  
Political Science ◽  
Experimental Studies ◽  
The United States ◽  
Syrian Refugees ◽  
New Model ◽  
Null Results ◽  
Research Designs ◽  
Incentive Problems ◽  
Cumulative Knowledge

A critical barrier to generating cumulative knowledge in political science and related disciplines is the inability of researchers to observe the results from the full set of research designs that scholars have conceptualized, implemented, and analyzed. For a variety of reasons, studies that produce null findings are especially likely to be unobserved, creating biases in publicly accessible research. While several approaches have been suggested to overcome this problem, none have yet proven adequate. We propose a new model in which scholars post short “null results reports” online that summarize their research designs, findings, and interpretations. We discuss a template for these reports and illustrate their utility with two experimental studies focused on the naturalization of immigrants in the United States and attitudes toward Syrian refugees in Jordan. We conclude with a discussion of how to overcome incentive problems and inculcate a discipline-wide norm of publicizing null findings.

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