the answer is reliable money. how much money would you pick up a verified 1 minute survey from the real u.s. government for? I'd do it for $5. (=$300 per hour) and hope for as many calls as possible.

For comparison purposes the U.S. budget is about $20,000 per person ($7t budget, a bit under 350m people), so the government could definitely pay you to answer their "spam" calls. (While mandating that first parties show that it is the real U.S. government and not a spammer.)

So it would be your actual first party telephone showing "Answer this real call from the U.S. government for $5 instantly, 1 minute average call time."

I think that would be a good way to get good data fast. What do you think? (At the same time, impersonating the U.S. government would remain illegal, and the first party would ensure the payment is real.)