Microsoft’s wizard wheeze of paying punters to use its search service appears to be paying off.

Under Microsoft’s Cashback program, launched in May, the company rewards shoppers with rebates from a few cents to $20 or more on items they find using its search engine, Live Search. When the company started the plan it said it would measure its success by the number of items advertised, growth in its share of searches that lead to transactions online, and how happy merchants are with returns on their investment in Cashback ads.

Now the bean counters have got the figures back, they are saying that Cashback seems to have been successful. Frederick Savoye, a senior director of product management for Live Search, said the number of items advertised on Cashback has grown to 13 million, from 10 million at launch.

More than  4.5 million people have been using Cashback every month since it started, and that the program has been effective in boosting Microsoft's overall search share.