Originally from the The SMAC Academy by buster
A pop boom means that your city increases 1 in size per turn - e.g. it goes from size 4 to size 6 in two turns.
To pop boom a city one needs:
+2 nutrients (that is two nutrients more than what the city consumes)
For most factions (Gaia, Uni, Believers, Sparta & PK). This can be achieved by:
Building a children's creche (+2 growth).
Choosing Democratic/Planned in Social Engineering (+2 growth each)
Once you have done this and provide the +2 nutrients by working nutrient rich squares or using crawlers to supply nutrients your city will take off in size. As long as above conditions are in place it will even grow during drone riots.
It will keep on growing one in size per turn until you either are unable to provide the +2 nutrients or you hit a limit where you need a facility (Hab complex or Hab dome) for the city to get larger.
Pop booming with Golden ages:
Some factions cannot achieve the +6 growth needed to pop boom until very late in the game when Eudamonia becomes available as a social engineering choice.
They are Hive (cannot use democracy) and Morgan (cannot use planned). Of the Smac-x factions they are Cyborgs (-1 growth), Pirates (-1 growth) and Usurpers (cannot use democracy).
In Smac-x you do however have another chance of acquiring the +6 growth which is to have the city enter a golden age (requires no drones and minimum half population is talents). Golden ages give +2 growth. This requires switching citizens to talents/transcends and/or boosting your psych allotment until the city is in Golden Age. A Golden Age is indicated with the city name in white on the F4 screen.
In classic smac pop booming with golden ages does not work - even with the patches installed.
To provide the city with the +2 nutrients use crawlers to gather nutrients Prevent drone riots from growth by assigning population to be specialists (thinkers & doctors or empaths will create help prevent drones) and/or allocating psych. As your cities will be growing rapidly it is wise to check each turn if next time it grows riots are likely.
The subjects of pop booms, usage of specialists, usage of crawlers and achieving golden ages are all closely related. Being able to juggle these factors is one of the main things separating the vets from the newbies.