The study looked at how foreign investment affects local businesses in 17 countries. They found that when foreign companies buy goods from local suppliers, it helps local businesses become more productive. However, when foreign companies are in the same industry or sell to local customers, it doesn't always have a positive impact. The strength of this effect varies depending on the industry, where the investment comes from, the country's business environment, how advanced the local businesses are technologically, the education level of workers, and other specific factors.