I'm with Ankit on this one - it is definitely NOT A MUST to memorize such stats and numbers. A case interview is not an exam that tests memorization skills.
That said, when a candidate comes across as generally knowledgeable, well-read about a market / general macroeconomic conditions in a given markets, it can definitely leave a strong impression and score plus points - typically lends a candidate a credibility & a more mature, experienced appearance. Also, it makes you life easier to come up with well-reasoned and fact-based assumptions in a case interview + increases efficiency - which is a critical factor to pass.
Having said that, if you are willing to put to go the extra mile, here are a few types of stats that can become very handy for all kinds of market sizings, profitability type questions, “free-flow” bigger picture conversations with a partner etc
- Economic: GDP per capita & growth, avg. individual & household incomes, CPI, income & corp tax rates
- Demographic: total population (e.g country & largest metro areas), avg. household size, life expectancy, avg. age & age distribution (esp for emerging markets → very distinct)
- Other (select): # of tourists / visitors per year, urbanization rate, % smart phone penetration, literacy rate
It's never a bad idea to develop a good feel for such numbers, at least for the local market where you're interviewing + maybe select globally-leading markets (e.g. US, EU, China). But again, no point in memorizing just for the sake of it.
I have a cheat sheet that captures stats for different key markets - do reach out via PM, if interested and/or if you'd like learn more on how to best use such data points to maximize case performance.
Hope this helps.