Extruder Performance Measurements

There are so many extruder designs, both drive and the hot-end, that are being proposed. How can the performance be measured?

It is difficult to optimize a design if there is not a measurement procedure.

To keep it simple, maybe something like:
XYZ design can @220 C continuously extrude more than NN grams of PLA /second using a 0.4mm nozzle in the air (not printing)

XYZ design can @220 C continuously extrude less than yy grams of PLA /second using a 0.4mm nozzle in the air (not printing) without getting pulgs or problems. This specification is for very small detailed object with a slow extrusion per layer to allow for cooling.

What existing specifications are there? What are other people and companies using?

There are no existing specifications like this and no measurement procedure. One reason for this is that there is no "reference" plastic that could be used to make repeatable measurements between different people. With PLA the differences between plastic brands, colours and batches are large and with ABS it's even worse.