  We study a more powerful variant of false-name manipulation in Internet
auctions: an agent can submit multiple false-name bids, but then, once the
allocation and payments have been decided, withdraw some of her false-name
identities (have some of her false-name identities refuse to pay). While these
withdrawn identities will not obtain the items they won, their initial presence
may have been beneficial to the agent's other identities. We define a mechanism
to be false-name-proof with withdrawal (FNPW) if the aforementioned
manipulation is never beneficial. FNPW is a stronger condition than
false-name-proofness (FNP).
