If the opposite were true, that low margins attract competition, then the margins would increase towards 100%. How do you tell if these companies are going towa

If the opposite were true, that low margins attract competition, then the margins would increase towards 100%. How do you tell if these companies are going towards 100% or 0%? Wouldn’t we need to see a change over time? How do you account for businesses which are acquired during that time which affect their margins?