FWIW - the median is probably not helpful for some of these trades when framed as they are here because it's not a simple salary gradient like you might find wi

FWIW - the median is probably not helpful for some of these trades when framed as they are here because it's not a simple salary gradient like you might find with say, l1-l8 software engineer. For example - master electrician vs journeyman electrician are very different - journeyman require supervision (ie are not allowed to work without it), master's don't. (I actually wonder if "first line supervisors ..." above includes master electricians, since they are required to supervise journeyman).