From an early age I've been constantly calculating various kinds of estimates - e.g. "how many people live in this building", "how long will it take to cross the US on foot", "what's the height of that tower", "how many BMWs are manufactured annually" and so on.

Did you do this spontaneously, or did your parents or teachers encourage you to?

Do you practice anything similar with your children?

Nope, but I will (once he's a bit older; at two and a half his grasp of "counting" is still limited).