(Sorry this took so long to answer.. but... The question is easy to ask, but more complicated to answer than our usual research topics!!
Our Challenge was..
1. During the past year, what have been the large movements of people across the world? (We're interested here in people who are moving from one place to another for economic, political, or safety reasons--not people going home temporarily for the New Year's or Thanksgiving Day celebrations.)
A. Find data sources that tell us how many people moved from location X to location Y in 2015?
B. Is there a good way to visualize that data? (Giant tables of numbers aren't all that descriptive, there must be a better way. Can you find a good one?)
C. How do you know that these numbers are right? And to what extent can you believe them? Why?
My thoughts on this: First, this is a HUGE problem. (Note to self--don't make such gigantic Challenges in the future! One could spend an unbounded amount of time on this. I also note that I probably should have asked for data from 2014, since some organizations still haven't published their 2015 data yet!)
To answer this in a reasonable amount of time, I'm going to focus on getting the Mexico/US migration data, and extend that to Syria refugees, and then wrap up with a couple of information visualizations.
Mexico/US Migrations: I live in California, one of the border states with Mexico. I was born in Los Angeles, and live now in Palo Alto, so the Mexican heritage runs fairly deep. As you know, migration across the border is a very contentious issue, which means that getting solid data might be a little tricky.
As Regular Reader Remmij said beautifully: "...events outpace data collection > factual accuracy is hard to come by > data is subject to manufacture/agenda manipulation > generalities outpace specifics >
perceived data outweighs ground truth in a media driven environment"
But let's give it a shot. Clearly, our strategy will have to be to triangulate the data from multiple sources.
I'll start with a query of:
[ migration data Mexico US ]
and limit the hits to the past year (using the Search Tool drop-down "Past Year"). By looking through the hits, it's clear that there are two main sources of immigration data--Pew Research and the Census.gov data on immigration.
As is obvious, there's a lot of debate about which data to trust. Some think tanks find much of the data in dispute (e.g., Austin Institute), and you can find extended debates about how the data is collected (is it accurate? what time period does it cover? what's the sampling method?).
But I know that both Pew and the Census.gov people try to do a reasonable job. So let's look at their data first.
Pew Research: In their article about Mexican migration give the following data:
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| Figure from Pew Research report on net migrations to/from Mexico. |
This chart only covers 1995 to 2014. (Notice also that the middle bars cover the years 2005 to 2010, while the bars on the right ALSO covers 2009 - 2014... in essence, they overlap by one year.) Still, you can see a trend beginning of net migration FROM the US to Mexico. You can read about their census methods in their Methodology article.
In summary, they get data from the Mexican government (National Survey of Demographic Dynamics (Encuesta Nacional de la Dinámica Demográfica—ENADID): 2014) and from the US Census (Current Population Survey (CPS): 2000-2014 March Annual Social and Economic Supplement (ASEC)). They do a fairly sophisticated analysis to get good estimates of the true number.
In a different article, Pew points out that the net migration (by year) between Mexico and the US is primarily in the direction of Mexico.
The article "More Mexicans Leaving than Coming to the US" they publish a telling chart (see below). This chart is based on the same dataset as above (NSDD, ENADID, US Census, etc.).
How does the Census.gov data compare?
I did a search like this:
[ migration US Mexico site:census.gov ]
and found the Census.gov site for International Programs (which has data for other countries, including migration rates in/out of the US).
Their key chart for this period (and a forecast out to 2025) is this:
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| Figure from Census.gov, International Program. |
Although it's not an exact copy of the Pew data, the trends agree: the net migration pattern is from the US to Mexico, not the other way around.
Exploring this idea of "finding a reliable source," I did a query for:
[ DHS Mexico US migration data ]
thinking that DHS (Department of Homeland Security) would have reliable data. And, unsurprisingly, I found their 2013 Handbook of Immigration Statistics.
This is really a compendium of all kinds of immigration data (including emigration for all kinds of reasons). But the relevant data are:
"Persons obtaining lawful residence by country of origin"
2013, Mexico: 134,198
"Persons naturalized, by country of origin"
2013, Mexico: 99,385
There are many other data tables here as well, including "Non-migrant temporary workers" and others that I'll skip since they're temporary status.
But the other factor is "Aliens apprehended by country of origin"
2013, Mexico: 424,978
If you keep looking through this resource, you'll get pretty darn close to the Pew estimate from above (of 870K immigrants during 2013). (And, FWIW, the historical trends duplicate the Pew findings--they're net towards Mexico!)
I thought of another data source that might be reliable: The UN. My query:
[ UN Mexico US migration data ]
led me to a large data-rich report on the total number of migrants from each country in the world. There I found a data table that reported that (overall) 1.1M Mexicans had emigrated to the US in 2015 (but didn't report on the number who left the US to go elsewhere). That's a little higher than the Pew estimate, but "only" by 200,000.
More importantly, this reference, International Migration Report, goes a long way towards answering our other question about large migrations across the world, as there's data for migration from every country. In the summary page, they write:
"Nearly two thirds of all international migrants live in Europe (76 million) or Asia (75 million). Northern America hosted the third largest number of international migrants (54 million), followed by Africa (21 million), Latin America and the Caribbean (9 million) and Oceania (8 million).
In 2015, two thirds (67 per cent) of all international migrants were living in just twenty countries. The largest number of international migrants (47 million) resided in the United States of America, equal to about a fifth (19 per cent) of the world’s total. Germany and the Russian Federation hosted the second and third largest numbers of migrants worldwide (12 million each), followed by Saudi Arabia (10 million)..."
Now that's interesting data, but like all migration data, you have to read it VERY carefully. These numbers are total migrants in a country not their own. In other words, this is the total number of migrants in country X, who might have moved there 20 years ago. This isn't the number of migrants in any one year.
However, there IS a data table for migrants in that were hosted by a country in 2000 and 2015 farther down in the UN report. This table shows the number of migrants in both years. The net immigration rate is (roughly) the difference between 2015 and 2000 divided by 15 (for the US, that's around 787K / year, which is in the ballpark with other figures we've seen).
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| Page 32 of the UN's International Migration Report, 2015. |
Visualizing the data:
As you might expect, for such a hot topic, there is a wealth of data and visualizations of that data to help understand what's going on. Of course, each visualization is only as good as its underlying data source.
As Ramon's query shows:
[ migration 2015 visualization ]
leads to a host of visualizations. Here are a couple (based on UN migration data).
From Lucify, showing comet trails of people migrating in Europe (click through to see the real interactive visualization):
And with a query much like the one above, Regular Reader Hans found a large number of infographics and data visualizations collected all on one page. See The Refugee Crisis through the eyes of Data Visualization. That's a great collection, here are four that I liked collaged together:
These can go on forever, but I found one that I really liked, both for its visualization properties, and the sense of the way the world migrations are interlocked. This is the visualization from PeopleMov.in by Carlo Zapponi. (you really have to click through to get the full experience). Gratefully he provided information about where he got his data. The main source of the data is the Bilateral Migration Matrix (the latest version is 2013) from the World Bank site which is a giant spreadsheet showing movement of people from country X to country Y.
A note of interpretation: As we saw above (but worth repeating here), the data set, and the visualization tool shows the estimate of “migrant stocks” in a given country as of 2010. (“Migrant stocks” are people who live in a country other than the one they were born in, including refugees. Note that these numbers are NOT the number of people crossing the border each year.) This matrix of data is what's being viewed here (click on any of these to see them full-size):
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| This shows the outflow (emigration) from Mexico to other countries. |
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| If you zoom way out, you can see emigrants from Mexico mostly end up in the US. |
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| If you click on the USA bar on the right side, you can see where immigrants to the US come from. Unsurprisingly, many are from Mexico, but there are many from other countries as well, such as the 1.7M from China and the 1.6M from India. |
If you take that data (immigration into the US during 2012), you can see that the majority of immigration into the US is from Mexico.
And with a little exploration, you can see there are a huge number of people moving from place to place...constantly.
Search Lessons
Answering this question took a LOT more time than I'd anticipated. It's easy to find data, but finding the RIGHT data is tricky. This experience led me to a few essential search insights:1. Check multiple sources. In my case, I looked at (and found) data from the UN, the Census Department, the DHS (Dept. Homeland Security), and Pew (which in turn drew from data sources in Mexico). Luckily, the data were pretty close together, though not in perfect agreement... which is to be expected.
2. The data is there, but you HAVE to read very carefully. As we saw above, there's a ton of data out there in various repositories--but the metadata describing the data sets always requires a great deal of careful attention to ensure that you've got the right data set, AND that it's actually what you think it is. (This probably explains why you can read such wildly varying reports of data in the news--it's easy, in the course of fast-paced research, to grab the first numbers that come across your screen. Especially for these controversial topics, it's essential to have a validation / double-checking step in place.
3. Visualizations are great... but be sure you understand what the data is from, and how it's transformed. Again, it's easy to mis-interpret what you see. And remember this basic axiom: If they don't report on where the underlying data comes from, you can't trust the infographic!
For Teachers
These kinds of assignments typically require a great deal of fairly sophisticated reading. As a way of getting students to talk about how/what they found, have different teams presenting their findings (including what queries they used, and what sources the found). This can be a lively discussion, especially as students start to hear about other kinds of research paths than the one they tried.
An important part of their search strategy will be getting data from particular resources (e.g., UN, UNHCR, DHS, Census, etc.) They need to learn how to recognize those names as well. (Think about it this way--a student who doesn't know about the UN won't think to search for that as a reliable data resource.) So be sure to teach the names of reliable data sources as well.
Search on!
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