This paper discusses accuracy of recording, allocating and valuing in the context of comparisons between farms of efficiency ratios and gross margins. Some experiments were conducted to investigate the effects on rank orderings of livestock gross margins of (i) different allocations of failures to reconcile between recorded sources and recorded uses of livestock, and (ii) of random changes in valuations of livestock. The outcome of the experiments suggests that inaccuracies which occur in farm recording, allocating and valuing can lead to wrong classifications of farms into groups for comparative purposes.