Hi,
Yes, market sizing questions are still widely used! I ran a specific course on market sizing and would be happy to help.
You should first focus on you segmentation skills:
B2C:
- Demographics (Age, education, income, family size, race, gender, occupation, nationality)
- Behavioral (Purchasing behavior, customer journey stage, occasion & timing,
customer loyalty & interest, risk tolerance, user status)
- Psychographic (Lifestyle, personality traits, values, opinions, interests of consumers)
- Geographic (Geographical boundaries)
B2B:
- Company characteristics (Industry, company size, number of employees)
- Geography (Geographical boundaries)
- Purchasing Approach (Occasion & timing, customer capabilities, nature of existing relationship)
- Personal Characteristics (Loyalty, risk attitude, user status)
B2G:
- Demographics (Type of agency, size of budget, the amount of autonomy)
- Geographic (Geographical boundaries)
- Government Tier (Federal , State, Local, Quasi-governmental, International)
- Bid type (Closed, Open)
But sometimes you don’t need to segmentation. Here is an example of case that could be solved with high level top down approach - estimate the size of credit card market in the US:
https://www.preplounge.com/en/consulting-forum/how-should-i-approach-the-following-question-estimate-the-market-size-of-credit-cards-in-the-us-6695
Best,
Anton