Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for selectively requesting bids from content item providers. In one aspect, a method includes selecting eligible content item providers that are eligible to respond to a next content request. Each of the eligible content item providers can be selected based, at least in part, on a response constraint that specifies a maximum rate at which the content item provider is able to receive content requests. Impression likelihood scores are determined for the eligible content item providers, and qualified content item providers are selected a set of the eligible content item providers are selected as qualified content item providers based on the impression likelihood scores. The impression likelihood score for each qualified content item provider meets a threshold impression likelihood score.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for increasing advertiser utility in broad match auctions. In one aspect, a method includes receiving, from an advertiser, a set of keywords; accessing a linear program for a keyword language auction; determining a solution to the linear program; determining, based on the solution to the linear program, a proper subset of the keywords that increases the advertiser's utility relative to the advertiser's utility for the set of keywords; and generating utility bids for each of the keywords in the subset, each utility bid corresponding to one of the keywords in the subset and being a bid price for the keywords.