  For a sample of 51 blazars with extensive optical polarization data, we used
circular statistics to calculate the scatter among the polarization position
angles for each object. We found that this scatter is correlated with the radio
core dominance. We compared this relationship with the predictions of a simple
transverse shock model. The result suggests that blazar jets are likely to
cover a wide range of speeds consistent with those derived from observations of
superluminal motion.
