The study looked at how trade agreements between countries affect firms from other countries—like Costa Rica's firms—using detailed data. The researchers found that some trade deals actually help companies from outside the agreement sell more to member countries. They discovered these agreements can make it easier for firms from other places to enter markets by making the rules more similar. This is especially helpful for companies selling products that need lots of regulation. So, deep trade agreements can have a good impact on firms in countries not part of the agreement by increasing their chances of exporting to member countries.