How a number with no source becomes a fact everyone knows
The country maps on this subject are mostly fiction, and they got there by a repeatable process. Once you can see the process, you cannot unsee it.
Search for a map of average penis size by country and you will find dozens. They are colourful, complete, confidently captioned, and they cover every country on earth.
There are not primary studies for every country on earth. There are not primary studies for most of them. So the maps are, necessarily, mostly invented. That they are wrong is the boring half. The interesting half is how a fabricated figure acquires the appearance of a fact, because the process is repeatable and you can watch it happen on other subjects once you know the shape of it.
Stage one: a gap and a format
It starts with demand meeting a format. People want a ranking, and a world map coloured by a variable is one of the most shareable objects on the internet.
But a map has a structural requirement that a table does not: it has to fill every country. A table can leave a row out. A map with grey patches looks broken, so the incentive is to produce a number for every territory whether or not one exists.
This is the original sin, and it happens before anyone has decided to deceive anybody. The format demands completeness and the data cannot supply it.
Stage two: filling the gaps
The gaps get filled by whatever is available. A self-reported survey. A figure from a neighbouring country. A regional average interpolated across borders. Occasionally a number that appears to have been generated to make the map look plausible.
At this stage the compilation may still be honest about itself, carrying a note that some figures are estimated. That note is the first thing lost.
Stage four: citation laundering
Now the compounding begins, and it is the stage that makes the number durable.
A content site writes an article about the map and cites the aggregator. A second site cites the first. A third cites the second. Within a few steps the number has half a dozen citations, none of which lead to a study, all of which lead to each other.
This is citation laundering, and it produces something that behaves exactly like a well-sourced fact. It has references. The references have references. Following any single one appears to confirm it. Only following all of them to the end reveals that the chain terminates in an aggregator that filled a gap.
The number is now unkillable, because refuting it requires demonstrating a negative about a source nobody can locate.
How to check any of this in two minutes
It works on this subject and on every other subject.
- Ask who measured, and how many. A real figure has a sample size and a method. A laundered one has neither, and the absence is the tell.
- Follow the citation, once. Not the claim, the link. If it goes to another article rather than to a study, follow it again. Two hops is usually enough to reach either a paper or a dead end.
- Look for suspicious completeness. A dataset with no gaps, on a subject where gaps are inevitable, is a dataset that has filled them.
- Check the precision. A figure given to two decimal places from a study of two hundred people is claiming precision the sample cannot support. Confident decimals on a shaky sample are a decoration.
- Notice what is adjacent. If the page carrying the number is also selling something the number makes you want, the number is advertising copy that has been formatted as data.
What honest coverage looks like instead
It looks worse. And that is the difficulty.
A country list built only from traceable primary studies covers a fraction of the world, disappoints anyone hoping to find their own country, and cannot be drawn as a complete map. It also has to admit that several of its rows come from small studies, that others used a different protocol, and that some of the gaps between adjacent countries are smaller than the gap between two measurement methods.
Every one of those admissions makes it less shareable and more true. That is the trade, and it is not a close call: a short list of sourced figures is worth more than a complete map of invented ones, even though the map will always travel further.
Hence the shape of this game. It covers the countries it can cover. Each row prints its study, its sample size and its method. A country whose widely circulated figure traces back to nothing is labelled as untraced, rather than quietly included to round out the set.
Before you go
This piece is published for general interest and education. It is not medical advice, and nothing in it is a substitute for speaking to a doctor. Every figure quoted is a population average from a published study, and the variation between individual men inside any one of those populations is far larger than any difference between them.
If something about your own body is worrying you, please take it to a clinician rather than to an article.
Sources
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