  The "standard" model of cosmology is founded on the basis that the expansion
rate of the universe is accelerating at present --- as was inferred originally
from the Hubble diagram of Type Ia supernovae. There exists now a much bigger
database of supernovae so we can perform rigorous statistical tests to check
whether these "standardisable candles" indeed indicate cosmic acceleration.
Taking account of the empirical procedure by which corrections are made to
their absolute magnitudes to allow for the varying shape of the light curve and
extinction by dust, we find, rather surprisingly, that the data are still quite
consistent with a constant rate of expansion.
