  The anomalous magnetic moments of both positive and negative muons are
measured to the precision of 0.7 parts per million. Two values are in good
agreement. The standard model calculations of muon g-2 are under further
studies, especially the descrepancies between $e^+e^-$ and $\tau$ data. The
differences between experimental result and the standard model calculations are
$2.4\sigma$ for $e^+e^-$ data and $0.9\sigma$ for $\tau$ data.
