Given the relatively high cost of Settlers, this Policy is very useful to cut down production time during your initial expansion period. As with other specific production-boosters, it would be nice to churn up several Settlers one after another; however remember that there is the small detail of the Population of the source city diminishing by 1 for every Settler produced (or Purchased)! So, maybe you should adopt Colonization only from time to time and produce one unit at a time, so as not to cripple your source city too much.
Civilopedia Entry Edit
The urge to procreate is a basic human trait, as true of civilizations as of individuals. In early times, these were usually established by maritime city-states on distant (relatively) shores; the Greeks and Phoenicians scattered them around the Mediterranean coasts in what they considered uninhabited lands. The Romans created colonial cities on the fringes of their empire across Western Europe, North Africa, and West Asia. Early Chinese dynasties pursued a similar policy. Through the troubled Middle Ages, the only people to undertake large-scale settling were the foot-loose Vikings, but once other Europeans began crossing the oceans they all started planting colonies all over the globe … and squabbling over who got what.