TAM (Total Addressable Market): the full annual revenue a product would earn if every possible buyer on Earth used it at the price you charge.
Uber's 2008 seed deck estimated the US taxi market at roughly $4.2B, with a global TAM of about $5B. By 2023, Uber alone did over $37B in revenue and the global ride-hailing market crossed $150B. The lesson VCs took from this: a credible bottom-up TAM beats a flashy top-down one, because real markets often expand once a product exists to serve them.
