Publishers trial paying peer reviewers – what did they find?

> Some 53% of researchers accepted the invitation to review when offered payment, compared with 48% of those who received a standard, non-paid offer. On average, paid reviews came in one day earlier than unpaid ones.

Does not sound like notable effects to either end. (I was once offered a payment for a peer review, but declined it.)

Don't overlook the other experiment's results.