We explore a transfer learning setting, in which a finite sequence of target concepts are sampled independently with an unknown distribution from a known family. We study the total number of labeled examples required to learn all targets to an arbitrary specified expected accuracy, focusing on the asymptotics in the number of tasks and the desired accuracy. Our primary interest is formally understanding the fundamental benefits of transfer learning, compared to learning each target independently from the others. Our approach to the transfer problem is general, in the sense that it can be used with a variety of learning protocols. The key insight driving our approach is that the distribution of the target concepts is identifiable from the joint distribution over a number of random labeled data points equal the Vapnik-Chervonenkis dimension of the concept space. This is not necessarily the case for the joint distribution over any smaller number of points. This work has particularly interesting implications when applied to active learning methods.