  We show that the leading power corrections to the event shape distributions
can be resummed into nonperturbative shape functions that do not depend on the
center-of-mass energy and measure the energy flow in the final state. In the
case of the thrust variable, the distribution is given by the convolution of
the perturbative spectrum with the shape function. Choosing the simplest ansatz
for the shape function we find that our predictions for the thrust distribution
provide a good description of the data throughout a wide range of energies.
