Investigation of the accuracy of search engine hit counts

This study investigates the accuracy of search engine hit counts for search queries. We investigate the accuracy of hit counts for Google, Yahoo and Microsoft Live Search, and the accuracy of single and multiple term queries. In addition, we investigate the consistency of hit count estimates for 15 days. The results show that all three provide estimates for the number of matching documents and the estimation patterns of their counting algorithms differ greatly. The accuracy of hit counts for multiple word queries has not been studied before. The results of our study show that the number of words in queries affects the accuracy of estimations significantly. The percentages of accurate hit count estimations are reduced almost by half when going from single word to two word query tests in all three search engines. With the increase in the number of query words, the error in estimation increases and the number of accurate estimations decreases.