Statistical studies over the last forty-five years show that, although there are success stories, very many mergers and acquisitions do not result in the increased operating profits that economics textbooks would lead one to expect. As consultancy McKinsey have put it, 'Anyone who has researched...

We construct a novel data set to show that, between 2003-2020, up to one-fifth of America's largest firms had a non-financial blockholder or insider as their largest shareholder. Blockholders and insiders tend to be less diversified than institutional investors. Measures of "universal" and...