We argue that, with respect to the number of segments firms report, this was the case to a great extent under SFAS No. 14 and is so to a lesser extent under the current SFAS No. 131.1 We therefore exploit the change to SFAS No. 131 segment reporting to examine two possible motives for discretionary nondisclosure (i.e., aggregation) of segments under SFAS No. 14, namely, proprietary costs and agency costs.