US terminal block market leaders

I am a Senior at a state university in Pennsylvania. I am writing a paper in my international marketing class on "The organization, distribution and market trends of NEMA/IEC terminal block industry". I have a good amount of data, however I cannot find information on how big the market leaders are in the US, or even who that #1 is. I know that the following 5 companies are large players: Allen Bradley, Phoenix Contact, WAGO, Weidmuler, and ABB. I would appreciate the insight and/or knowledge anyone could provide.