What do Amazon reviews really do? The research

The first five reviews change a product's purchase likelihood by up to 270% — no other lever on a listing has this effect per euro spent.

The Spiegel study: why the first reviews count most

The Spiegel Research Center at Northwestern University examined in 2017 how online reviews change purchase decisions. The central finding: the jump from zero to the first reviews is the biggest single effect a listing ever experiences. A product showing its first five reviews is bought with up to 270% higher likelihood than the same product without reviews. After that the curve flattens — every further review helps, but with diminishing returns. For sellers this means: the most expensive listing is one sitting at zero.

The sweet spot: 4.0 to 4.7 — and why perfect profiles hurt

The same study found a result that surprises many: purchase likelihood peaks in the star range of roughly 4.0 to 4.7. A flawless 5.0 profile reads as implausible to buyers — too smooth to be real. Critical voices among the positive ones are not a flaw but proof the reviews come from real people. That is exactly why we at Lutendo do not filter out 4-star reviews: they are the strongest authenticity signal a listing can have.

Volume beats average — up to a point

Research on the so-called popularity bias adds to this (Powell et al. 2017, Psychological Science): buyers often pick the product with more reviews, even if its average is merely solid. A larger count reads as reliability — many people bought it, it cannot be that wrong. In practice: a credible average in the sweet spot plus visible volume beats a thin perfect profile.

What this means for launches

New products start at zero — against competitors with hundreds of voices. The research makes the priority clear: build the first verified reviews first, because that is where the biggest effect lies. After that, continuity counts. A tester campaign makes exactly this first step predictable — with real purchases, honest reviews and automatic verification.

Start a campaign for the first reviews →

All third-party figures with sources; exact values vary by category and market. Nothing on this page promises a review or a ranking — the offer is honest, verified reviews.