It is difficult for organizations introducing and using software inspections to evaluate how efficient they are. However, it is of practical importance to determine whether they have been efficiently implemented or whether further corrective actions are necessary to bring them up to standard. We present in this paper a procedure for building inspection efficiency benchmarks based on simulation and typical inspection data. Based on most of the data published in the literature, we build an industry-wide benchmark which intends to capture the current practice regarding inspection efficiency. This benchmark construction procedure can also be used to build enterprise specific benchmarks. Last, we assess how robust we can expect them to be by distorting their input distributions to reflect violations of the assumptions made.