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Not obvious to me, but it means Total Fertility Rate. From wikipedia, TFR of a population is basically the average number of children that would be born to a woman over her lifetime.

Total fertility rate

One single Google search would have revealed that TFR means Total Fertility Rate.

I did this of course, lets say:

Transferrin receptor, Temporary Fly restriction, Terrain Following Radar, Time Frequency Representation

And a Truck in Thailand is named TFR also...

Actual problem is that writing "TFR" or "Total Fertility Rate" takes a constant time (independent from the number of readers) while everyone looking it up is function of the number of readers.

Your parent comment is right in pointing out that it is not a familiar abbreviation.

I suspect people use obscure acronyms like this as a signal that they're familiar with the problem domain and that you should listen to them.