  The goal of this paper is to examine experimental progress in laser wakefield
acceleration over the past decade (2004-2014), and to use trends in the data to
understand some of the important physical processes. By examining a set of over
50 experiments, various trends concerning the relationship between plasma
density, accelerator length, laser power and the final electron beam en- ergy
are revealed. The data suggest that current experiments are limited by
dephasing and that current experiments typically require some pulse evolution
to reach the trapping threshold.
