8. A non-transitory computer readable medium storing instructions that upon execution by one or more data processing apparatus cause the one or more data processing apparatus to perform operations comprising: identifying an opportunity to provide a content item having distribution criteria matching a phrase of one or more words; determining that the phrase matches each of a first distribution criterion and a second distribution criterion that are used to distribute content for a given content sponsor; determining that a first match between the first distribution criterion and the phrase is a more specific match than a second match between the second distribution criterion and the phrase; determining that the first distribution criterion is associated with a first bid that is lower than a second bid associated with the second distribution criterion; in response to determining that the first match is more specific that the second match and that the first bid is lower than the second bid, reducing the second bid by a specified amount to obtain a reduced bid; selecting one of the first distribution criterion or the second distribution criterion as a winning distribution criterion based, at least in part, on the first bid and the reduced second bid; and providing data specifying the winning distribution criterion.
8. A non-transitory computer readable medium storing instructions that upon execution by one or more data processing apparatus cause the one or more data processing apparatus to perform operations comprising: identifying an opportunity to provide a content item having distribution criteria matching a phrase of one or more words; determining that the phrase matches each of a first distribution criterion and a second distribution criterion that are used to distribute content for a given content sponsor; determining that a first match between the first distribution criterion and the phrase is a more specific match than a second match between the second distribution criterion and the phrase; determining that the first distribution criterion is associated with a first bid that is lower than a second bid associated with the second distribution criterion; in response to determining that the first match is more specific that the second match and that the first bid is lower than the second bid, reducing the second bid by a specified amount to obtain a reduced bid; selecting one of the first distribution criterion or the second distribution criterion as a winning distribution criterion based, at least in part, on the first bid and the reduced second bid; and providing data specifying the winning distribution criterion. 9. The computer readable medium of claim 8 , wherein reducing the second bid by a specified amount comprises reducing the second bid to a value that is equal to or less than the first bid.