Query performance prediction

Machine logic that traces increases (or decreases) in query drift by performing the following steps: retrieving a first response list responding to a first query; retrieving a second response list responding to a second query, wherein the second query is based, at least in part, on a topic related to the first query; determining a set of scores for each of the first response list and the second response list, calculating a normalized query commitment ("NQC") for each of the first response list and the second response list; and responsive to determining that a ratio representing a relative difference between the NQC for the first response list and the NQC for the second response list is above a predetermined threshold, determining to use the second response list to respond to the first query.