  We present late-time radio observations of 68 local Type Ibc supernovae,
including six events with broad optical absorption lines (``hypernovae''). None
of these objects exhibit radio emission attributable to off-axis gamma-ray
burst jets spreading into our line-of-sight. Comparison with our afterglow
models reveals the following conclusions: (1) Less than $\sim 10%$ of Type Ibc
supernovae are associated with typical gamma-ray bursts initially directed away
from our line-of-sight; this places an empirical constraint on the GRB beaming
factor of $<f_b^{-1}> \lesssim 10^4$ corresponding to an average jet opening
angle, $\theta_j \gtrsim 0.8$ degrees. (2) This holds in particular for the
broad-lined supernovae (SNe 1997dq, 1997ef, 1998ey, 2002ap, 2002bl and 2003jd)
which have been argued to host GRB jets. Our observations reveal no evidence
for typical (or even sub-energetic) GRBs and rule out the scenario in which
every broad-lined SN harbors a GRB at the 84% confidence level. Their large
photospheric velocities and asymmetric ejecta (inferred from spectropolarimetry
and nebular spectroscopy) appear to be characteristic of the non-relativistic
supernova explosion and do not necessarily imply the existence of associated
GRB jets.
