Researchers studied why companies decide to combine or stay separate. They focused on transaction costs, which are the expenses of making deals, and how firms try to lower these costs by choosing the best way to organize and make contracts. They found that incomplete contracts, unique assets, and trust problems influence firms' decisions on whether to integrate vertically or not. It's like companies trying to save money and fix issues by picking the right structure to work with others. Studies back up these ideas, showing they make sense in real-world situations. Other theories suggesting differences in risk-taking made little impact compared to transaction cost ideas.