In this paper, they talk about how public and private money can work together to fund important projects like building bridges and roads. They studied how the set-up of financial deals affects this collaboration. By looking at real project data, they found that there is a balance needed between the cost of services and how much help the government gives to make projects happen. They highlighted that changes in economic and legal rules can affect which type of funding is best. Interestingly, they discovered that countries in the middle-income range tend to use the most private money for big projects. So, finding the right mix of public and private funding is crucial for making these projects successful.