  Formation rates of compact-object binaries are often derived from population
synthesis calculations. However, such calculations depend sensitively on a
relatively large number of model input parameters. Given considerable
uncertainty in those model parameters, the predicted inspiral rates for double
compact objects relevant to gravitational-wave interferometric detectors have
been shown to be are uncertain by several orders of magnitude. Typically,
inspiral rates are estimated for only a small set of models with a remarkably
poor coverage of the highly multi-dimensional parameter space (primarily
because of limited computer resources). Here, using as an example seven
population-synthesis model parameters, we show that it is possible to derive
fits of double-compact-object inspiral rates dependent simultaneously on all
seven parameters. We find these fits to be accurate to 50% for binary black
holes and to 40% for binary neutron stars. The availability of such fits
implies that (i) depending on the problem of interest, it is not necessary to
complete large numbers of computationally demanding population synthesis
calculations; and (ii) for the first time, the sufficient exploration of the
relevant phase space and the assessment of the uncertainties involved is not
limited by computational resources and becomes feasible. Finally, we have also
produced a histogram of the (a priori likely) binary black hole inpsiral rate,
assuming our population synthesis models are equally likely. This histogram,
effectively an a priori probability distribution for the BH-BH inspiral rate,
suggests that merger rate is conservatively bounded below by
10^(-8)/yr/Milky-Way-galaxy.
