market sizing usually doesn’t require much information to be memorized. The main data I would recommend to know are:
- State populations, in particular for the area you live in. So for Europe, knowing the population of Spain, UK, France, Italy Germany, Russia and the main countries in Eastern Europe would help.
- Formulas for volume/surface of solid figures - sphere, cylinder, pyramid, parallelepiped, cone.
Knowing the number of companies in your own country could also come handy if you end covering something related to that.
As mentioned, once you know the previous data, you should be able to estimate all the other numbers with an appropriate justification.