  It has been suggested that the effects of renormalization significantly
reduce the amplitude of the inflationary spectra at scales measurable in the
cosmic microwave background. Via a gauge-invariant analysis, we compute the
renormalized scalar and tensor power spectra and follow their evolution in an
inflating universe that undergoes a transition to an FRW phase with a growing
horizon. For perturbations originating from Minkowski vacuum fluctuations, we
show that the standard prediction for the spectra on superhorizon scales is a
late-time attractor, while they are UV finite at all times. Our result is
independent of the equation of state after inflation, showing that the standard
prediction is fully robust.
