brucet - 4:56 pm on Jan 4, 2008 (gmt 0)

I came across these stats from Revoo. They are a third-party provider of product review functionality, but their figures make perfect sense and I've no reason to doubt them.

- Positive reviews double the sales of a product among customers who read them
- Negative reviews halve the sales of a product among customers who read them
- Overall, adding reviews leads to a 1.9x increase in sales from customers who read them

There appear to be several reasons why the overall effect is so positive:

1) The presence of reviews increases consumer confidence and makes them more likely to buy
2) The overwhelming majority of reviews tend to be positive, with only a few negative and almost no neutral ones.
3) A negative review doesn't stop people buying from the site - it only stops them buying that particular product. They just find a similar product with a more positive review and buy that instead. This is called 'purchase substitution'.

Hope this helps