Value Sort for Amazon

Overview

It reads only what the page has rendered; nothing is fetched or sent anywhere. It's available for Firefox on Firefox Add-ons; the Chrome version is in review at the Chrome Web Store. The code is on GitHub.

What It Does

• Rating: It pulls ratings toward a fixed baseline of 4.3 stars, weighted by default as 30 reviews, so a 4.9 from a handful of reviews doesn't outrank a 4.5 from thousands. The weight can be changed under Advanced in the panel.
• Price: It uses the per-unit price Amazon prints on each result, when most results on the page share a unit, so a large pack is compared fairly with a small one. Otherwise it uses the list price, and the panel says which it chose. Where a result shows no per-unit price, it estimates one from the title and marks it “est”.
• Hidden, not removed: Sponsored results, products under a chosen review count, and results it can't price on the page's basis are dimmed and moved down. Switching sorting off restores Amazon's order.

What Was Measured

• Price, rating, review count, unit price and the sponsored flag were read correctly wherever they appeared, across five saved amazon.com searches. Each value was checked against a second, independent read of the same result.
• A live check on three searches passed.
• Checked against Amazon's own per-unit price, the title estimate agrees on 77% of results where it finds a quantity (135 of 175). Most misses under-count multi-packs, so the estimate comes out too high and the product sinks — the estimates hide good deals rather than promoting bad ones. The 77% is measured on results that publish a unit price, which are plausibly the better-formatted listings, so it is an optimistic bound rather than a neutral estimate of how the estimate does where it is actually used.
• A live check on amazon.co.uk (with a UK delivery address), amazon.ca, amazon.com.au, amazon.sg and amazon.in also worked.

What’s Weak

• Title estimates: Sellers write titles, and the parser misreads multi-packs. On searches ranked per item, a pack count can also be read as the number of items. Anything marked “est” is worth a glance before trusting.
• It only sees the current page: It ranks the results loaded, not the whole search.
• Selectors drift: It depends on Amazon's page markup, which changes without notice.
• English sites only: On other Amazon sites, star ratings would read as missing and the quality half of the slider would do nothing, so they are switched off rather than left silently broken.
• “Per load” isn't a fixed amount: Detergent is priced per load, and a medium load and a large load are ranked as the same unit.
• Nothing measures whether it helps: It re-orders results for whoever installs it, but nothing is randomized or measured, so it says nothing yet about whether shoppers end up better off.