In the study, they looked at why regional trade grows, focusing on agriculture trade between certain countries that are part of trade groups like NAFTA, Mercosur, EU, and APEC. Agriculture trade is chosen because it was protected in rich countries and not in poor ones. The researchers found that factors affecting how much countries trade were often studied, but not enough focus was on why trade grows. They discovered that as neighboring countries have more trade, they also change their trade policies to become more open. This shift then leads to more trade with nearby countries and eventually the formation of trade deals. The researchers saw that regional trade tends to grow faster than global trade, even before specific trade agreements are made.