the premise of your question is already wrong.

there's a world of different between resource law and irb.

in fact, we should move away from the much abused term 'mid size' because it (i) doesn't indicate anything about the quality of the firm relative to its peers in its core practice areas, (ii) is often used as a proxy for anything that's not Big 4, and (iii) places undue emphasis on size. technically, Hoh Law and many chinatown / toa payoh firms can be considered mid size (no offence to them).

so your question is like asking: what's the typical GDP per capita of a non-OECD country? well, there's singapore, and then there's zimbabwe.