  Large differences between the properties of the known sample of cataclysmic
variable stars (CVs) and the predictions of the theory of binary star evolution
have long been recognised. However, because all existing CV samples suffer from
strong selection effects, observational biases must be taken into account
before it is possible to tell whether there is an inconsistency. In order to
address this problem, we have modelled the impact of selection effects on
observed CV samples using a Monte Carlo approach. By simulating the selection
criteria of the Palomar-Green (PG) Survey, we show that selection effects
cannot reconcile the predictions of standard CV evolution theory with the
observed sample. More generally, we illustrate the effect of the biases that
are introduced by magnitude limits, selection cuts in U-B, and restrictions in
galactic latitude.
