Recent Publications

Data on stocks and flows of international migration are necessary to understand migrant patterns and trends and to monitor and evaluate migration-relevant international development agendas. Many countries do not publish data on bilateral migration flows. At least six methods have been proposed recently to estimate bilateral migration flows between all origin-destination country pairs based on migrant stock data published by the World Bank and United Nations. We apply each of these methods to the latest available stock data to provide six estimates of five-year bilateral migration flows between 1990 and 2015. To assess the resulting estimates, we correlate estimates of six migration measures from each method with equivalent reported data where possible. Such systematic efforts at validation have largely been neglected thus far. We show that the correlation between the reported data and the estimates varies widely among different migration measures, over space, and over time. We find that the two methods using a closed demographic accounting approach perform consistently better than the four other estimation approaches.
In Scientific Data, (6) 82.,2019

Despite the lack of robust empirical evidence, a growing number of media reports attempt to link climate change to the ongoing violent conflicts in Syria and other parts of the world, as well as to the migration crisis in Europe. Exploiting bilateral data on asylum seeking applications for 157 countries over the period 2006–2015, we assess the determinants of refugee flows using a gravity model which accounts for endogenous selection in order to examine the causal link between climate, conflict and forced migration. Our results indicate that climatic conditions, by affecting drought severity and the likelihood of armed conflict, played a significant role as an explanatory factor for asylum seeking in the period 2011–2015. The effect of climate on conflict occurrence is particularly relevant for countries in Western Asia in the period 2010–2012 during when many countries were undergoing political transformation. This finding suggests that the impact of climate on conflict and asylum seeking flows is limited to specific time period and contexts.
In Global Environmental Change, 54, 239–249,2019

An indirect estimation method is used to derive country to country migration flows from changes in global bilateral stock data. Estimates are obtained over five- and 10-year periods between 1960 and 2015 by gender, providing a comprehensive picture of past migration patterns. The estimated total of global international migrant flows generally increases over the 55-year time frame. The global rate of migration over five- and 10-year periods fluctuate at around 0.65 and 1.25 percent of the population, respectively. The sensitivity of estimates to alternative input stock and demographic data are explored.
In International Migration Review, 52 (3), 809–852.,2018

Little attention is given to the role of migration in global population projection models. Most demographers set future levels of net migration on trajectories towards zero in all countries, nullifying the impact of migration on long-run projected populations. Yet as fertility and mortality rates fall, the role of migration on future population change is becoming more pronounced. In this paper we develop future long-run migration scenarios to provide a range of possible outcomes. Our alternative migration scenarios are linked to the Shared Socioeconomic Pathways (SSP), widely used in research on global environmental change. These are utilized as inputs for a global cohort component projection model to obtain population totals up until 2100 for all countries. The results illustrate the important role of migration assumptions in long run projections, especially in post demographic transition countries. Further, they provide plausible alternatives to projections based on the commonly used, but poorly justified, convergence to the zero net migration assumption
In Demographic Research, 38 (54) 1635–1662.,2018

Within one generation, the South Korean economy developed from one of the poorest countries in the world during the 1950s to a developed, high-income country by the end of the 1990s. During the latter part of this period, South Korea (hereafter called Korea) experienced rapid demographic change characterized by a steep decline in fertility levels and abnormally high sex ratios at birth. Unlike other East and South-East Asian countries that underwent similar economic and demographic changes, Korea has witnessed a steady decline in the sex ratios at birth since the end of 1990s through 2000s. In this paper, we visualize the current spatial distribution of population born during the peak years of sex ratios at birth.
In Environment and Planning A: Economy and Space, 50 (5), 941-944.,2018

In comparison with other developed nations, there is a relative lack of analyses on internal migration flow in South Korea. During the last 50 years, the country has witnessed distinct changes in both the levels and patterns of internal migration. Traditionally, the faster developing north-west administrative units (Seoul, Incheon and Gyeonggi regions) have accounted for the majority of in-migration. However, since 2011, internal migration in Korea has become more diffuse, with migrants moving to a greater variety of regions. We visualize these changes using chord diagram plots.
In Regional Studies, Regional Science, 5(1).,2018

We adapted the chord diagram plot to visualize China’s recent inter-provincial migration during 2010–2015. The arrowheads were added to present the direction of the flows. This method allows us to show the complete migration flows between 31 provinces in China including the direction and volume of the flows. The spatial component was also clearly depicted in the plot using four color palates representing four regions in China (i.e. East, Center, West, Northeast) and arranging the 31 provinces in an approximate geographic order. Besides that, we extend the chord diagram plot to describe China’s bilateral net migration during 2010–2015.
In Environment and Planning A, 49(11).,2017

The relationship between climate change and human migration is not homogenous and depends critically on the differential vulnerability of population and places. If places and populations are not vulnerable, or susceptible, to climate change, then the climate-migration relationship may not materialize. The key to understanding and, from a policy perspective, planning for whether and how climate change will impact future migration patterns is therefore knowledge of the link between climate vulnerability and migration. However, beyond specific case studies, little is known about this association in global perspective. We therefore provide a descriptive, country-level portrait of this relationship. We show that the negative association between climate vulnerability and international migration holds only for countries least vulnerable to climate change, which suggests the potential for trapped populations in more vulnerable countries. However, when analyzed separately by life supporting sector (food, water, health, ecosystem services, human habitat, and infrastructure) and vulnerability dimension (exposure, sensitivity, and adaptive capacity), we detect evidence of a relationship among more, but not the most, vulnerable countries. The bilateral (i.e., country-to-country) migration show that, on average, people move from countries of higher vulnerability to lower vulnerability, reducing global risk by 15%. This finding is consistent with the idea that migration is a climate adaptation strategy. Still, ~6% of bilateral migration is maladaptive with respect to climate change, with some movement toward countries with greater climate change vulnerability.
In Sustainability, 9(5), 720,2017

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Introduction The tidycat package includes the tidy_categorical() function to expand broom::tidy() outputs for categorical parameter estimates. Documentation For full documentation, see the package vignette: The tidycat package: expand broom::tidy() output for categorical parameter estimates Hello World The tidy() function in the broom package takes the messy output of built-in functions in R, such as lm(), and turns them into tidy data frames. library(dplyr) library(broom) m1 <- mtcars %>% mutate(transmission = recode_factor(am, `0` = "automatic", `1` = "manual")) %>% lm(mpg ~ transmission + wt * as.


Over the last year or so I have been playing around with different ways of showing changing global bilateral migrant stocks, adapting the animation code I created for the plots for region to region flows in this estimation paper. I am putting them online here in case they are of interest to anyone else. Feel free to download the plots using right click over the animation and then Save Video as or from Github.


We have had a number of requests for the R code to replicate the plots in our paper on internal migration in China. The code below will produce a similar looking plot, but I have taken out some of the arguments that were very specific to our plot that will not replicate well for other data. Data The code is based on two data sets: Bilateral flow data with three columns only (origin, destination and flow), see here for the file used below Region details used for plotting, see here for the file used below Note, the names in the region data are the same as the ones used in the origin and destination data.


During the last few months I have given some introductory talks on international migration in Asia and Europe. I had a couple of requests to share the animated chord diagrams that I created for others to use in their teaching materials. These are below, along with some extra plots for Africa, the Americas (Northern, Central and Southern America as well as the Caribbean) and Oceania. Feel free to download the plots using right click over the animation and then Save Video as or from Github.


Background I’m loving the magick package at the moment. Reading through the vignette I spotted the image_morph() function. In this post I experiment with the function to build the GIF below that shows the changes in the England football first kit over time, using images from the excellent Historical Football Kits website. Scraping The Historical Football Kits website has a detailed section on England kits spread over six pages, starting from the first outfits used in 1872.


Recent & Upcoming Talks

Bilateral International Migration Flow Estimates for 200 Countries
21 January 2020 2:00 PM
Bilateral International Migration Flow Estimates for 200 Countries
27 July 2019 3:00 PM
European International Migration Patterns
13 July 2018 2:00 PM
Driving Factors of Asian International Migration Flows
13 July 2018 11:15 AM
Probabilistic Method for Combining Internal Migration Data
07 June 2018 9:20 AM
Probabilistic Method for Combining Internal Migration Data
04 May 2018 12:30 PM
Visualizing Migration Flows: How to Design and Produce Animated Directional Chord Diagrams in R
01 May 2018 12:00 PM
Driving Factors of Asian International Migration Flows
26 April 2018 8:30 AM
Gender, Education and Marital Status Differentials in Migration
22 February 2018 12:00 PM
Gender, Education and Marital Status Differentials in Migration
09 February 2018 3:00 PM


ARDI International Migration Pillar

Exploring international migration patterns for the Globe, Asia and Shanghai.

Combining Migration Data

Combining traditional and emerging big data sources to model population. Funded by Der Jubiläumsfonds der Stadt Wien für die Österreichische Akademie der Wissenschaften.

Global Migration Predictions

The Prediction of Future Migration Patterns for Improved Global Population Projections. Funded by National Science Foundation of China Research Fund for International Young Scientists.


Currently Teaching at Shanghai University:

  • 3XS371026 Data Science with R, Semester 1, 2019-20
  • 3XS371022 Statistical Modelling with R, Semester 3, 2019-20


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