  It has been suggested that the peculiar properties of the luminous Type Ic
supernova SN 1998bw and its low-energy gamma-ray burst GRB 980425 may be
understood if they originated in a standard gamma-ray burst explosion viewed
far from the axis of the relativistic jet. In this scenario, strong radio
emission is predicted from the jet on a timescale 1 to 10 years after the
explosion as it decelerates and spreads into our line of sight. To test this
hypothesis we have carried out late-time radio observations of SN 1998bw at
$t=5.6$ years, yielding upper limits which are consistent with the continued
fading of the supernova. We find these limits to be consistent with an off-axis
jet only if the progenitor mass loss rate is $\dot{M}\lesssim 4 \times 10^{-7}$
M$_\odot$ yr$^{-1}$ (for a wind velocity $v_w=1000$ km s$^{-1}$) or the
fraction of the shock energy in magnetic fields is $\epsilon_B \lesssim
10^{-3}$. These values are low relative to those inferred for cosmological
GRBs. We combine the SN 1998bw measurements with existing observations for a
sample of 15 local Type Ibc supernovae to estimate that at most 6% produce
collimated, relativistic outflows.
