This paper defines the notion of unbiased aggregation of inputs and provides a necessary and sufficient condition for this to apply.

In this note we investigate the power of significance test for dummy variables in the context of Simar and Wilson (2007) two-stage efficiency analysis model.

The discussion about the bias due to input (or output) aggregation in efficiency measurement based on data envelopment analysis, recently revisited by Tauer (2001) and Fare and Zelenyuk (2002) is continued. Attention is focused on the direction and the bounds of the aggregation bias.

This note shows that the Nerlovian profit indicator may be aggregated over firms into an industry measure of profit efficiency. The note also provides conditions under which the technical component of the indicator may also be aggregated.