Economy (Industry) is a gameplay mechanic in Age of Civilizations 2. Each province has its own economic level. For example, the economy level of Constantinople in the 1440 scenario is 21716 while the economy of London in that same scenario is 3012. The economy level of a province can be increased by manually investing gold, spending movement points, or by the Economy Interface by increasing the investments slider, spending more money to increase economy, each turn by a bit. If one lowers the investments bar below a certain level, the economy level decreases, much like population decreases with the goods bar. If the population is too high compared to the economy, the increase from manual investment stagnates.
Economy growth can be increased by the map editor. If the economy is 99, then to increase the economy, the population needs to be decreased into the thousands. Otherwise, it cannot be increased.