Very little? Actually, it's not too little. Basically, some big cows in a certain field also do projects in the background of other disciplines, because no one will do things that are purely theoretical but can't be applied to other disciplines (especially physics and computers, and there are too many related topics. )。 The reason why we don't call those people economists in other disciplines is probably because their contributions in mathematics are higher than those in other fields (although their contributions in other fields may be high).