  The redshift distribution of gamma-ray bursts (GRBs) is strongly biased by
selection effects. We investigate, via Monte Carlo simulations, one possible
selection effect that may be modifying the Swift GRB redshift distribution. We
show how telescope response times to acquire a GRB redshift may, via the
Malmquist effect and GRB optical afterglow brightness distribution, introduce a
bias into the average of the observed redshift distribution. It is difficult to
reconcile a recently reported correlated trend between telescope response time
and average redshifts unless we employ a redshift-dependent optical afterglow
distribution. Simulations of this selection effect suggest that GRB optical
afterglows may have been either intrinsically brighter early in the Universe or
suffered less local host galaxy extinction.
