  We investigate what current cosmological data tells us about the cosmological
expansion rate in a model independent way. Specifically, we study if the
expansion was decelerating at high redshifts and is accelerating now, without
referring to any model for the energy content of the universe, nor to any
specific theory of gravity. This differs from most studies of the expansion
rate which, e.g., assumes some underlying parameterised model for the dark
energy component of the universe. To accomplish this, we have devised a new
method to probe the expansion rate without relying on such assumptions.
  Using only supernova data, we conclude that there is little doubt that the
universe has been accelerating at late times. However, contrary to some
previous claims, we can not determine if the universe was previously
decelerating. For a variety of methods used for constraining the expansion
history of the universe, acceleration is detected from supernovae alone at >5
sigma, regardless of the curvature of the universe. Specifically, using a
Taylor expansion of the scale factor, acceleration today is detected at >12
sigma. If we also include the ratio of the scale of the baryon acoustic
oscillations as imprinted in the cosmic microwave background and in the large
scale distribution of galaxies, it is evident from the data that the expansion
decelerated at high redshifts, but only with the assumption of a flat or
negatively curved universe.
