Method

This site tells readers to check who produced a figure. That applies here first.

Four source types, labelled in the sentence

Peer-reviewed. Published in a journal with methods described. Rare in this field, and the Stanford hybrid-work study in Nature is the one this site leans on. For a related reference, see this overview.

Professional body. SHRM and equivalents, serving a practitioner membership — the constraint that makes them more reliable than vendors on cost benchmarks.

Survey organisation. Gallup and equivalents. Large samples, published methodology, no solution being sold.

Vendor. Employee experience platforms, monitoring companies, HR software firms. Frequently large samples and real work, arriving at a product. Labelled at every use.

How each is used

Peer-reviewed findings are stated as findings.

Professional body figures are used for arithmetic, because you can apply them to your own numbers.

Survey figures are given with the population.

Vendor figures give direction and their magnitude is attributed to them — a vendor reporting that poor management raises turnover is describing something real, and the multiple is a number produced by somebody selling manager development.

Ranges rather than points

50–200% of salary. Roughly 14% additional attrition.

Presented as ranges because they are ranges, and because the variation by role and sector is larger than the precision the point figure implies.

Arithmetic shown

Where a claim rests on a calculation, the calculation is on the page so you can substitute your own headcount, salary and turnover.

The practical pages end in a measurement you run rather than a conclusion you accept.

What is never done

No product named in an evaluative context.

No outcome promised.

No HR or legal advice, since the consequences of getting that wrong land on somebody who is not the reader.

And no figure without its type, which is the single rule this site would be least defensible without.

Limits

Seven of them have their own page, including how much of the underlying research generalises beyond large US organisations.

For additional context on this topic, see 500px.