  We discuss the impact of special relativistic effects on the observed light
curves and variability duty cycles of AGNs. We model the properties of AGN
light curves at radio wavelengths using a simulated shot noise process in which
the occurrence of major flaring events in a relativistic jet is governed by
Poisson statistics. We show that flaring sources whose radiation is highly
beamed toward us are able to reach very high flux levels, but will in fact
spend most of their time in relatively low flaring states due to relativistic
contraction of flare time scales in the observer frame. The fact that highly
beamed AGNs do not return to a steady-state quiescent level between flares
implies that their weakly beamed counterparts should have highly stable flux
densities that result from a superposition of many long-term, low-amplitude
flares. The ``apparent'' quiescent flux levels of these weakly beamed AGNs
(identified in many unified models as radio galaxies) will be significantly
higher than their ''true'' quiescent (i.e., non-flaring) levels. We use Monte
Carlo simulations to investigate flux variability bias in the selection
statistics of flat-spectrum AGN samples. In the case of the Caltech-Jodrell
Flat-spectrum survey, the predicted orientation bias towards jets seen end-on
is weakened if the parent population is variable, since the highly beamed
sources have a stronger tendency to be found in low flaring states. This effect
is small, however, since highly beamed sources are relatively rare, and their
fluxes tend to be boosted sufficiently above the survey limit such that they
are selected regardless of their flaring level. We find that for larger
flat-spectrum AGN surveys with fainter flux cutoffs, variability should not be
an appreciable source of selection bias.
