The cumulative reaction probabilities of Schatz for Cl + HCl, I + HI, and I + DI are analyzed by averaging them over an energy interval wider than the trapped state and rotational threshold structures and narrower than the quantized transition-state spacings. This analysis shows that the total reactivity is dominated by short-time dynamics in these cases and clearly reveals quantized transition-state structure underlying the other features. In all three cases we present a spectroscopic fit to the transition-state spectrum, and we compare the spectroscopic constants to those extracted from a variational transition-state theory analysis based on the adiabatic theory of reactions.