In Europa Universalis II, the neighbor bonus is a stream of technological direct investment that a country receives for free, simply by being lower tech than its neighbors. "Neighbors" in this sense is a bit obscure: it is not physically bordering countries, but rather, sets of countries (called techgroups; see below) that are established by the game. When one country in a techgroup gets ahead, its progress tends to "drag up" all the other countries in its techgroup, especially smaller countries that are more than 2 levels behind.