68% and 95% likelihood contours on the model Schechter parameters for our UV (rest-frame ~1700 Å) LF determination at z ~ 7 (magenta lines) and z ~ 8 (dotted red lines). For comparison, we also include the LF determinations at z ~ 4 (blue lines), z ~ 5 (green lines), and z ~ 6 (cyan lines) from Bouwens et al. (2007). We do not include the z ~ 8 contours in the center and right panels given the large uncertainties on the z ~ 8 Schechter parameters. It is striking how uniform the rate of evolution in the UV LF (left and middle panels) is as a function of redshift—though there is a significant degree of degeneracy between ϕ* and M*. Most of the evolution in the LF appears to be in M* (particularly from z ~ 7 to z ~ 4). Within the current uncertainties, there is no evidence for evolution in ϕ* or α (rightmost panel).