  We use a variant of principal component analysis to investigate the possible
temporal evolution of the dark energy equation of state, $w(z)$. We constrain
$w(z)$ in multiple redshift bins, utilizing the most recent data from Type Ia
supernovae, the cosmic microwave background, baryon acoustic oscillations, the
integrated Sachs-Wolfe effect, galaxy clustering, and weak lensing data. Unlike
other recent analyses, we find no significant evidence for evolving dark
energy; the data remains completely consistent with a cosmological constant. We
also study the extent to which the time-evolution of the equation of state
would be constrained by a combination of current and future-generation surveys,
such as Planck and the Joint Dark Energy Mission.
