Top: abundances observed in comets versus gas-phase abundances observed in young protostars. Middle and bottom: abundances observed in comets versus total abundances (gas and ice) from our model at t = t_acc. All abundances are relative to n_H. For the observational data points, the error bars indicate the spread between sources. For the model data, they indicate the range of values across the entire disk (middle) or the comet-forming region (bottom). Dotted error bars indicate the full range extends to less than 10^-12. The diagonal dotted lines represent hypothetical one-to-one relationships between abundances on the x and y axes.