  The paper proposes a parsimonious and flexible semiparametric quantile
regression specification for asymmetric bidders within the independent private
value framework. Asymmetry is parameterized using powers of a parent private
value distribution, which is generated by a quantile regression specification.
As noted in Cantillon (2008) , this covers and extends models used for
efficient collusion, joint bidding and mergers among homogeneous bidders. The
specification can be estimated for ascending auctions using the winning bids
and the winner's identity. The estimation is in two stage. The asymmetry
parameters are estimated from the winner's identity using a simple maximum
likelihood procedure. The parent quantile regression specification can be
estimated using simple modifications of Gimenes (2017). Specification testing
procedures are also considered. A timber application reveals that weaker
bidders have $30\%$ less chances to win the auction than stronger ones. It is
also found that increasing participation in an asymmetric ascending auction may
not be as beneficial as using an optimal reserve price as would have been
expected from a result of BulowKlemperer (1996) valid under symmetry.
