You probably meant top-down vs bottom-up. An example of top-down analysis is to go to e.g. Gartner or similar research firms and read that they estimate the ri

You probably meant top-down vs bottom-up. An example of top-down analysis is to go to e.g. Gartner or similar research firms and read that they estimate the ridesharing market to be say $100B. An example of bottom-up is to say, based on data from this and this article or data source, we estimate there are 1M cars doing ridesharing every year in the US. We will sell each of them a gadget for $10 so our market is $10M if we capture all of it.