Tim Harford's Undercover Economist has examples of how to get people to self select: https://www.goodreads.com/book/show/70420.The_Undercover_Economist https:/

Tim Harford's Undercover Economist has examples of how to get people to self select: https://www.goodreads.com/book/show/70420.The_Undercover_Economist https://www.goodreads.com/book/show/70420.The_Undercover_Eco...