  We study the question of setting and testing reserve prices in single item
auctions when the bidders are not identical. At a high level, there are two
generalizations of the standard second price auction: in the lazy version we
first determine the winner, and then apply reserve prices; in the eager version
we first discard the bidders not meeting their reserves, and then determine the
winner among the rest. We show that the two versions have dramatically
different properties: lazy reserves are easy to optimize, and A/B test in
production, whereas eager reserves always lead to higher welfare, but their
optimization is NP-complete, and naive A/B testing will lead to incorrect
conclusions. Despite their different characteristics, we show that the overall
revenue for the two scenarios is always within a factor of 2 of each other,
even in the presence of correlated bids. Moreover, we prove that the eager
auction dominates the lazy auction on revenue whenever the bidders are
independent or symmetric. We complement our theoretical results with
simulations on real world data that show that even suboptimally set eager
reserve prices are preferred from a revenue standpoint.
