Heterogeneity, Spatial Population Dynamics, and the Migration Rate

The literature on the impacts of heterogeneity and selection in population analysis has been limited largely to the conventional unistate perspective in which only decrements are considered; and their temporal (selectivity) impacts on independent subpopulations examined. In this paper, the focus is on the evolutionary dynamics of (multistate) multiregional populations whose interdependent subpopulations can experience increments as well as decrements. It is shown that in such instances migration rates that are not true occurrence-exposure rates are ambiguous, because they depend on the relative weightings existing during the initial model-fitting period. Net migration rates, lifetime migration rates, and return migration proportions all are imperfect measures of migration propensities, and their use as input measures to an analysis should be avoided whenever possible.

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The 2000-2010 Changes in Labor Market Incorporation of Return Mexican Migrants

Revista Latinoamericana de Población ◽

10.31406/relap2019.v13.i1.n24.6 ◽

2019 ◽

Vol 13 (24) ◽

pp. 135-162 ◽

Cited By ~ 2

Author(s):

Edith Y. Gutiérrez Vázquez

Keyword(s):

Labor Market ◽

Informal Economy ◽

Return Migration ◽

Migration Rate ◽

Job Market ◽

Return Migrants ◽

Mexican Migrants ◽

Net Migration ◽

The Past ◽

Internal Migrants

Mexico-U.S. migration has dramatically changed in the past three decades: the pronounced increasing flow of the 1990s stalled in the 2000s and a zero net migration rate was officially reported in 2010. Deportations and economic crisis have been discussed as the underlying reasons of this change. In the context of involuntary movements, I evaluate the labor market incorporation of return migrants with respect to non-movers and internal migrants in Mexico between 2000 and 2010. Using the Mexican Census samples, I found that the reduction on return migrants’ earnings is associated to changes in both, the characteristics of returnees and in the pay rates. Specifically, changes in their occupations and higher participation in informal economy are the most important differences associated to the earnings loss of return migrants. These findings suggest that return migration in involuntary contexts restrict resources that individuals use to incorporate in the job market upon returning.

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Brain drain and brain gain in Russia: Analyzing international migration of researchers by discipline using Scopus bibliometric data 1996–2020

Scientometrics ◽

10.1007/s11192-021-04091-x ◽

2021 ◽

Author(s):

Alexander Subbotin ◽

Samin Aref

Keyword(s):

Brain Drain ◽

Policy Development ◽

Donor Country ◽

International Mobility ◽

Science System ◽

Migration Rates ◽

Net Migration ◽

Novel Approach ◽

Five Disciplines ◽

The Impact

AbstractWe study international mobility in academia, with a focus on the migration of published researchers to and from Russia. Using an exhaustive set of over 2.4 million Scopus publications, we analyze all researchers who have published with a Russian affiliation address in Scopus-indexed sources in 1996–2020. The migration of researchers is observed through the changes in their affiliation addresses, which altered their mode countries of affiliation across different years. While only 5.2% of these researchers were internationally mobile, they accounted for a substantial proportion of citations. Our estimates of net migration rates indicate that while Russia was a donor country in the late 1990s and early 2000s, it has experienced a relatively balanced circulation of researchers in more recent years. These findings suggest that the current trends in scholarly migration in Russia could be better framed as brain circulation, rather than as brain drain. Overall, researchers emigrating from Russia outnumbered and outperformed researchers immigrating to Russia. Our analysis on the subject categories of publication venues shows that in the past 25 years, Russia has, overall, suffered a net loss in most disciplines, and most notably in the five disciplines of neuroscience, decision sciences, mathematics, biochemistry, and pharmacology. We demonstrate the robustness of our main findings under random exclusion of data and changes in numeric parameters. Our substantive results shed light on new aspects of international mobility in academia, and on the impact of this mobility on a national science system, which have direct implications for policy development. Methodologically, our novel approach to handling big data can be adopted as a framework of analysis for studying scholarly migration in other countries.

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Upstream and downstream morphodynamic influence in simulated and real meandering rivers

10.5194/egusphere-egu21-4561 ◽

2021 ◽

Author(s):

Hossein amini ◽

Guido Zolezzi ◽

Federico Monegaglia ◽

Emanuele Olivetti ◽

Marco Tubino

Keyword(s):

Migration Rate ◽

Machine Learning Techniques ◽

Stochastic Gradient Descent ◽

Support Vector ◽

Lateral Migration ◽

Remotely Sensed Data ◽

Meandering Rivers ◽

Meandering River ◽

Migration Rates ◽

Meander Migration

This study investigates the dependency of meander lateral migration rates on the spatial distribution of channel centerline curvature in both synthetic and real meandering rivers. It employs Machine Learning techniques (hereafter ML) to relate observed local lateral meander migration rates with the local and the upstream/downstream values of the centerline curvature. To achieve this goal, it was primarily essential to identify the feasibility of using ML in the meandering river's morphodynamics. We then determined the ability of ML to predict the excess near bank velocity based a set of input data using different regression techniques (linear and polynomial, Stochastic Gradient Descent, Multi-Layer Perceptron, and Support Vector Machine). We then moved forward to study the upstream-downstream influence on local migration rate. Synthetic meandering river planforms, as obtained through the planform evolution model of Bogoni et al. (2017), which is based on Zolezzi and Seminara (2001) meander flow model, were used as test cases for the calibration and check of the different adopted ML algorithms. The calibrated algorithms were then applied to multi-temporal information on meander planform dynamics obtained through the PyRiS software (Monegaglia et al., 2018), to quantify to which extent the upstream and downstream distribution of meander centerline curvature affects the local meander migration rate in real rivers.References&#160;1- Zolezzi, G., & Seminara, G. (2001b). Downstream and upstream influence in river meandering. Part 1. General theory and application overdeepening. Journal of Fluid Mechanics, 438(September 2015), 183&#8211;211. https://doi.org/10.1017/S002211200100427X2- Monegaglia, F., Zolezzi, G., G&#252;neralp, I., Henshaw, A. J., & Tubino, M. (2018). Automated extraction of meandering river morphodynamics from multitemporal remotely sensed data. In Environmental Modelling & Software (Vol. 105, pp. 171&#8211;186). https://doi.org/10.1016/j.envsoft.2018.03.0283- Bogoni, M., Putti, M., & Lanzoni, S. (2017). Modeling meander morphodynamics over self-formed heterogeneous floodplains. In Water Resources Research (Vol. 53, Issue 6, pp. 5137&#8211;5157). https://doi.org/10.1002/2017wr0207264- Benozzo, D.,&#160; Olivetti, E., Avesani, P. (2017). Supervised Estimation of Granger-Based Causality between Time series. In Frontiers in Neuroinformatics.&#160;https://doi.org/10.3389/fninf.2017.00068&#160;5- Sharma A., Kiciman, E. (2020). DoWhy: An End-to-End library for Causal Inference. arXiv preprint arXiv:2011.04216.&#160;https://arxiv.org/abs/2011.04216

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On the Persistence of U.S. Net Migration Rates in the 20th Century

Growth and Change ◽

10.1111/j.1468-2257.1981.tb00690.x ◽

1981 ◽

Vol 12 (4) ◽

pp. 43-49 ◽

Cited By ~ 3

Author(s):

DONALD B. PITTENGER

Keyword(s):

20Th Century ◽

Migration Rates ◽

Net Migration

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Estimating migration rates from two tag–release/one recovery experiments

ICES Journal of Marine Science ◽

10.1016/j.icesjms.2004.01.006 ◽

2004 ◽

Vol 61 (5) ◽

pp. 821-828 ◽

Cited By ~ 2

Author(s):

Kunio Shirakihara ◽

Shuichi Kitada

Keyword(s):

Experimental Design ◽

Coefficient Of Variation ◽

Migration Rate ◽

Skipjack Tuna ◽

Survey Area ◽

Time Intervals ◽

Migration Rates ◽

Movement Rates ◽

Recovery Techniques ◽

Tag Shedding

Abstract We propose a method for estimating migration (movement) rates from two tag–release/one recovery experiments, regardless of tag-shedding or incomplete tag-reporting which are major problems when tag–recovery techniques are applied to commercially exploitable populations. The entire survey area is divided into multiple strata in advance. The first release is limited to one stratum; then, the second release occurs in every stratum. Recoveries from both releases occur in every stratum. The migration rate between the time of the first and second release is estimated together with its variance. To check the applicability of our method, we applied it to tag–recovery data for skipjack tuna from various places at different times and unequal time intervals. The precision of the estimates was low and the coefficient of variation was 22.6–42.1% because of the small number of recoveries. The experimental design necessary to improve precision is discussed.

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