How long did it take to build the Chinese Wall?

So while this sounds like a classic market sizing, knowing a bit about the reality, they clearly fail in this case. There is no one wall, but many different parts, partly connected, partly not, made with different technologies, mud walls, wodden pallisades, bricks, etc...with hundreds of years in between construction, supervised by different cultures, using different technologies.

But in order to be helpful here, you'd want to estimte length, widths, height, maybe split the lengths into parts that are built on different terrain (e.g. 300 km from Tianjin to the border of inner mongolia with 50% hilly terrain, x km through dessert & grassland, etc. and assume different building speeds. That would get you to a number of person-years of building time.

Then you can assume number of available workers, estimate and come up wiht a rough estimation of how long it took them to build the wall.

Hi there,

You'll really get the best out of this exercise if you try it yourself. Why don't you post what you're thinking and we can help?

Hint: Do you think this makes more sense top-down or bottom up?

General Tips

Remember that there's rarely a "best" answer with market sizing. What's important is that you break down the problem the way it makes sense to you. Importantly, break it down so that the assumptions you make are the ones you're most comfortable in.

For example, do you know all the major brands? Great go with that. Do you understand all the segments of that country's population (either age or wealth or job breakdown)? Go with that. Do you know the total market size of a similar industry? Then break it down that way.