It doesn't matter whether it's possible for a highly motivated and educated person to distinguish the lemons. This will usually be true. The important thing is the experience of real consumers participating in the market as it actually exists. A better framing would be "of all products in category X sold last month on amazon, what fraction were lemons?"
csallen|5 months ago
It does though, since the entire premise of the "lemon market" idea is that buyers can't differentiate between good and bad products. What matters is where the bar is to be a good differentiator, and how many people can cross it.
It also doesn't necessarily matter how many lemons are for sale, if the good ones are easy to find. Imagine that there are 1 million trashy sleep masks on Amazon and only 3 good ones, but the 3 good ones are right at the top, with superior ratings and reviews.
The better question is: what % of buyers are buying lemons?