A method, including submitting, to a search engine, a first query including, and receiving, in response to the first query, a first list including first results, each of the first results having a respective first ranking. Keywords are derived from the first query, and for each keyword, a respective second query is submitted to the search engine, the respective second query including the first query term and the derived keyword. In response to each of the respective second queries, a respective second list including respective second results is received, each of the respective second results having a second ranking and a corresponding first result, and for each given second result, one or more stability scores are computed based on the second ranking of the given second result and the first ranking of the corresponding first result. The second results are ranked based on their respective one or more stability scores.