Perlman, E. S.E. S.PerlmanPadovani, P.P.PadovaniLandt, H.H.LandtGiommi, PaoloPaoloGiommi2020-09-172020-09-172001-01-01https://hdl.handle.net/20.500.13025/62Blazar Demographics and Physics, ASP Conference Series, Vol. 227. Edited by Paolo Padovani and C. Megan Urry. San Francisco Astronomical Society of the Pacific. ISBN 1-58381-059-5, p.200The rareness of blazars, combined with the previous history of relatively shallow, single-band surveys, has dramatically colored our perception of these objects. Despite a quarter-century of research, it is not at all clear whether current samples can be combined to give us a relatively unbiased view of blazar properties, or whether they present a view so heavily affected by biases inherent in single-band surveys that a synthesis is impossible. We will use the coverage of X-ray/radio flux space for existing surveys to assess their biases. Only new, deeper blazar surveys approach the level needed in depth and coverage of parameter space to give us a less biased view of blazars. These surveys have drastically increased our knowledge of blazars' properties. We will specifically review the discovery of ``blue'' blazars, objects with broad emission lines but broadband spectral characteristics similar to HBL BL Lac objects.conference paperhttp://adsabs.harvard.edu/abs/2001ASPC..227..200P2001ASPC..227..200P