This paper reports a systematic review of empirical studies concerning the effectiveness of elicitation techniques, and the subsequent aggregation of empirical evidence gathered from those studies. The most significant results of the aggregation process are as follows: (1) Interviews, preferentially structured, appear to be one of the most effective elicitation techniques; (2) Many techniques often cited in the literature, like card sorting, ranking or thinking aloud, tend to be less effective than interviews; (3) Analyst experience does not appear to be a relevant factor; and (4) The studies conducted have not found the use of intermediate representations during elicitation to have significant positive effects. It should be noted that, as a general rule, the studies from which these results were aggregated have not been replicated, and therefore the above claims cannot be said to be absolutely certain. However, they can be used by researchers as pieces of knowledge to be further investigated and by practitioners in development projects, always taking into account that they are preliminary findings.