  The recent Chandra image of the Crab nebula shows a striking, axisymmetric
polar jet. It is shown that jets are formed in axisymmetric, magnetized pulsar
winds and that the jet luminosity scales relative to the total as
(\gamma_0\sigma_{eq})^{-4/3}, where \sigma_{eq} is the ratio of Poynting flux
to particle kinetic energy output at the equator at the base of the flow and
\gamma_0 the initial Lorentz factor of the flow. The results are applied to the
image of the Crab nebula, and the limit is set for the Crab pulsar of
\sigma_{eq} \leq 100. It is argued that conventional pulsar theory needs to be
reexamined in light of these limits.
