When to "adjust" and when not to "adjust".

This is a cautionary tale, specifically about a "standard" principle that should not be standard, and can actually be misleading. It's often stated that you have to adjust events by population sizes, or you will get distorted impressions. For example, if you compare the number of house fires in two regions, you need to adjust by the number of houses in each region to give a realistic impression. You don't, not if what you explicitly want to show are the actual numbers of events. Of course, it would be dishonest to use those raw numbers to infer risk. Risk requires local background adjustments, but you don't always want to show a risk-like outcome. For example, if we look at migration data from tne United Nations (limited to the most recent year in that dataset, the 2019 report, which reports for 2018) and adjust the net migration (immigration minus emigration) by population, we get the following outcomes, expressed as percent of population"

Net Migration per Population

Time for a quiz. Which countries gained the greatest number of people? How about this, did the USA have more or fewer individual people immigrating (minus emigration) than did Qatar? You can't tell from this map or from any of the data included with it. There is no way you can use this map or its data to answer either of those questions. If you want to answer those questions, which are about numbers, not proportions or percentages, you have to look at the unadjusted numbers.

Net Migration, people

Now it's easier to answer questions of "how much", "how many", and "most". Even though the USA is near the middle of the pack when it comes to percent population migration outcomes, it is the undisputed top net recipient of migration. Likewise, while China and India look like they have very little net migration effect (which is true in terms of per population), they among the countries having the greatest numbers of population loss. They simply have the reserve to apparently absorb it better. Long story, short: Adjust by adjustments that are sensible. Both questions are sensible questions, but they are different questions and can't be answered by one map.