Two products, same category. One has 4.6 stars across 8,000 reviews. The other has 4.4 stars across 2,100 reviews — and Amazon says 3,000 people bought it last month. Which is the safer buy? We’d take the second one, most days, and this post is about why.
Star ratings are a lagging indicator
A star rating is an average over the product’s entire life. Those 8,000 reviews may be concentrated in 2022, when the product was current, well-priced, and actively supported. The listing keeps its shiny 4.6 while the product ages out, the seller stops answering support emails, or a quiet revision swaps components. Ratings decay slowly; products decay fast.
Review counts also compound survivorship: a listing that sold heavily years ago keeps its mountain of reviews forever, and shoppers keep reading that mountain as if it described the product on sale today.
Purchase velocity is a leading indicator
Amazon’s “bought in past month” figure — shown on many listings — is close to the opposite. It doesn’t care how the product did historically. It answers one question: are people choosing this product right now, at its current price, against its current competition?
That number quietly encodes a lot of due diligence other shoppers did for you. Current buyers saw today’s price, today’s alternatives, and today’s reviews — including the recent ones mentioning the quality drop — and bought anyway or didn’t. Strong current velocity on a mature product usually means the price is right and the product still delivers.
It’s also much harder to fake
Review manipulation is an industry: buy the product, get reimbursed, leave five stars. But faking purchase velocity means actually generating thousands of real orders every month, indefinitely — which is just called selling. A seller can sculpt their rating; they can’t easily sculpt sustained sales volume at scale.
How we use both
We don’t ignore ratings — a low rating with meaningful review volume is a hard fail in our screen, because enough owners voted and the vote is no. But between two well-rated products, we weight current demand heavily: it’s the freshest, least-gameable signal available. That’s why our product cards show the bought-last-month figure right next to the stars whenever Amazon exposes it, and why “most reviewed” and “best rated” are separate sorts on every category page — they genuinely rank different things.
The two-signal habit
The takeaway as a shopping habit: read the stars for quality, read the purchase velocity for relevance. A great rating with dead sales is a museum piece. Decent rating, strong monthly demand? That’s the product the market is actually choosing — and the market checks more spec sheets than any of us.