How much of an impact do reviews and ratings have on online sales? Does the number of reviews and ratings matter? Are reviews and ratings more important for higher-priced products/services?

Northwestern University's Spiegel Research Center and PowerReviews recently tackled those questions in an in-depth research study.

The researchers examined detailed data from two online retailers of primarily lower-priced product categories and a third online retailer of higher-priced gifts to determine the relationship between reviews/ratings and purchase behavior (see the full report for the complete methodology).

Including reviews on product pages measurably boosts sales, and conversion rates steadily rise with the first few pieces of feedback, the analysis found.