The $H_0$ Olympics: A fair ranking of proposed models
  Despite the remarkable success of the $\Lambda$Cold Dark Matter
($\Lambda$CDM) cosmological model, a growing discrepancy has emerged (currently
measured at the level of $\sim 4-6 \sigma$) between the value of the Hubble
constant $H_0$ measured using the local distance ladder and the value inferred
using the cosmic microwave background and galaxy surveys. While a vast array of
$\Lambda$CDM extensions have been proposed to explain these discordant
observations, understanding the (relative) success of these models in resolving
the tension has proven difficult -- this is a direct consequence of the fact
that each model has been subjected to differing, and typically incomplete,
compilations of cosmological data. In this review, we attempt to make a
systematic comparison of sixteen different models which have been proposed to
resolve the $H_0$ tension (spanning both early- and late-Universe solutions),
and quantify the relative success of each using a series of metrics and a vast
array of data combinations. Owing to the timely appearance of this article, we
refer to this contest as the ''$H_0$ Olympics''; the goal being to identify
which of the proposed solutions, and more broadly which underlying mechanisms,
are most likely to be responsible for explaining the observed discrepancy
(should unaccounted for systematics not be the culprit). This work also
establishes a foundation of tests which will allow the success of novel
proposals to be meaningful ''benchmarked''.
