About

Fifty-three notes on reading marketplace sales rank data, written for analysts, sellers and anyone who has been handed a rank chart and asked what it means.

What this covers

What the number measures. How to read a series without being misled by seasonality, stock-outs or your own noise floor. How to collect and store the data so it stays useful. How the marketplace mechanics produce the movements. What the data can be applied to, and the questions where the honest answer is that it cannot help.

There is no product and nothing to buy. Where commercial tools are discussed, it is in terms of the questions worth putting to them.

The archive, and what was left out

This domain previously ran a sales rank tracking service between 2007 and 2015. Five pieces written by that site have been kept, in a separate section, with their original dates and a notice on each explaining that the figures are historical.

Other material from the same period has not been kept, and it is worth saying why. The previous site also ran a paid review service: an author paid a fee, wrote a review of their own book, and it was published as site content. The sales page described the benefit as search visibility and links rather than as an editorial opinion.

Republishing those pieces would present paid promotional placement as editorial writing, which misleads the reader. It would also amount to hosting purchased links, which search engines now act against. Keeping them with a "paid placement" label would be honest and would remove any reason to keep them.

The five pieces that remain were written by the site's own editorial side, about products they did not sell, using their own data.

How the notes are written

Uncertainty is stated. Every estimation method here has wide error and the notes say so, with ranges rather than points.

Confounders come before conclusions. Availability, price, seasonality and market movement are checked before anything interesting is claimed.

The limits are explicit. One note is entirely a list of questions this data cannot answer, with what to use instead.

Corrections

Marketplace mechanics change and some of this will date. If something is wrong, please say so.

Contact: [add address before launch]