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We compare the set of local galaxies having dynamically measured black holeswith a large, unbiased sample of galaxies extracted from the Sloan Digital SkySurvey. We confirm earlier work showing that the majority of black hole hostshave significantly higher velocity dispersions sigma than local galaxies ofsimilar stellar mass. We use Monte-Carlo simulations to illustrate the effecton black hole scaling relations if this bias arises from the requirement thatthe black hole sphere of influence must be resolved to measure black holemasses with spatially resolved kinematics. We find that this selection effectartificially increases the normalization of the Mbh-sigma relation by a factorof at least ~3; the bias for the Mbh-Mstar relation is even larger. Our MonteCarlo simulations and analysis of the residuals from scaling relations bothindicate that sigma is more fundamental than Mstar or effective radius. Inparticular, the Mbh-Mstar relation is mostly a consequence of the Mbh-sigma andsigma-Mstar relations, and is heavily biased by up to a factor of 50 at smallmasses. This helps resolve the discrepancy between dynamically-based blackhole-galaxy scaling relations versus those of active galaxies. Our simulationsalso disfavour broad distributions of black hole masses at fixed sigma.Correcting for this bias suggests that the calibration factor used to estimateblack hole masses in active galaxies should be reduced to values of fvir~1.Black hole mass densities should also be proportionally smaller, perhapsimplying significantly higher radiative efficiencies/black hole spins. Reducingblack hole masses also reduces the gravitational wave signal expected fromblack hole mergers.

Selection bias in dynamically-measured super-massive black hole samples: its consequences and the quest for the most fundamental relation