Identifying inadequate search content

1. A computer-implemented method, comprising:

receiving, by a data processing device, data specifying a search query that was submitted by a user;

determining, by a data processing device, a particular search topic with which the search query is associated;

obtaining a measure of relevance of a topic corpus to the particular search topic;

obtaining a topic search volume value for the particular search topic based on a value indicative of a number of received search queries that correspond to the particular search topic;

determining, by the data processing device, a topic corpus quality measure for the particular search topic based on the measure of relevance and the topic search volume value;

determining, by the data processing device, that the particular search topic with which the search query is associated is classified as an underserved topic based on the topic corpus quality measure being less than a specified threshold value; and

providing, by the data processing device and in response to receiving the search query, data that cause presentation of a notification that the search query is associated with an underserved topic.

2. The method of claim 1 , further comprising:

receiving new content for the underserved topic;

determining that the new content increases the relative topic corpus quality measure for the underserved topic; and

compensating a provider of the new content based on the increase to the relative topic corpus quality measure.

3. The method of claim 2 , wherein determining that the new content increases the topic corpus quality measure comprises determining that the new content increases the relevance measure for documents that are included in the topic corpus for the underserved topic.

4. The method of claim 2 , further comprising determining a value of the compensation to the provider, the value of the compensation being determined based on a demand for the underserved topic and the topic corpus quality measure of the underserved topic.

5. The method of claim 1 , further comprising:

obtaining topic corpus quality measures for other search topics that have topic search volumes that are within a threshold value of the topic search volume for the particular search topic; and

determining the threshold value based on the topic corpus quality measures for the other search topics.

6. The method of claim 1 , further comprising:

obtaining topic search volume values for other search topics that have topic corpus quality measures that are within a threshold value of the topic corpus quality measure for the particular search topic;

determining a threshold search volume value based on the search volume values for the other search topics;

determining that the topic search volume for the particular search topic exceeds the threshold search volume value; and

classifying the particular search topic as an underserved topic.

7. A system comprising:

a data store storing relevance measures for documents that are included in a topic corpus for a particular search topic and a query search volume value for queries that have been identified as associated with the particular search topic;

one or more computers configured to interact with the data store, the one or more computers further configured to perform operations comprising:

receiving data specifying a search query that was submitted by a user;

determining that the search query is associated with the particular search topic;

obtaining a measure of relevance of a topic corpus to the particular search topic;

obtaining a topic search volume value for the particular search topic based on a value indicative of a number of received search queries that correspond to the particular search topic;

determining a topic corpus quality measure for the particular search topic based on the measure of relevance and the topic search volume value;

determining that the particular search topic is classified as an underserved topic based on the topic corpus quality measure being less than a specified threshold value; and

providing, in response to receiving the search query, data that cause presentation of a notification that the search query is associated with an underserved topic.

8. The system of claim 7 , wherein the one or more computers are further configured to perform operations comprising:

receiving new content for the underserved topic;

determining that the new content increases the topic corpus quality measure for the underserved topic; and

compensating a provider of the new content based on the increase to the relative topic corpus quality measure.

9. The system of claim 8 , wherein determining that the new content increases the topic corpus quality measure comprises determining that the new content increases the relevance measure for documents that are included in the topic corpus for the underserved topic.

10. The system of claim 8 , wherein the one or more computers are further configured to perform operations comprising determining a value of the compensation to the provider, the value of the compensation being determined based on a demand for the underserved topic and the topic corpus quality measure of the underserved topic.

11. The system of claim 7 , wherein the one or more computers are configured to perform operations further comprising:

obtaining topic corpus quality measures for other search topics that have topic search volumes that are within a threshold value of the topic search volume for the particular search topic; and

determining the threshold value based on the topic corpus quality measures for the other search topics.

12. The system of claim 7 , wherein the one or more computers are configured to perform operations further comprising:

obtaining topic search volume values for other search topics that have topic corpus quality measures that are within a threshold value of the topic corpus quality measure for the particular search topic;

determining a threshold search volume value based on the search volume values for the other search topics;

determining that the topic search volume for the particular search topic exceeds the threshold search volume value; and

classifying the particular search topic as an underserved topic.

13. A memory device encoded with a computer program comprising instructions that when executed cause one or more computers to perform operations comprising:

receiving data specifying a search query that was submitted by a user;

determining a particular search topic with which the search query is associated;

obtaining a measure of relevance of a topic corpus to the particular search topic;

obtaining a topic search volume value for the particular search topic based on a value indicative of a number of received search queries that correspond to the particular search topic;

determining, by a data processing apparatus, a topic corpus quality measure for the particular search topic based on the measure of relevance and the topic search volume value;

determining that the particular search topic with which the search query is associated is classified as an underserved topic based on the topic corpus quality measure being less than a specified threshold value; and

providing, in response to receiving the search query, data that cause presentation of a notification that the search query is associated with an underserved topic.

14. The memory device claim 13 , further comprising instructions that cause the one or more computers to perform operations comprising:

receiving new content for the underserved topic;

determining that the new content increases the topic corpus quality measure for the underserved topic; and

compensating a provider of the new content based on the increase to the topic corpus quality measure.

15. The memory device of claim 14 , wherein determining that the new content increases the topic corpus quality measure comprises determining that the new content increases the relevance measure for documents that are included in the topic corpus for the underserved topic.

16. The memory device of claim 14 , further comprising instructions that cause the one or more computers to perform operations comprising determining a value of the compensation to the provider, the value of the compensation being determined based on a demand for the underserved topic and the topic corpus quality measure of the underserved topic.

17. The memory device of claim 13 , further comprising instructions that cause the one or more computers to perform operations comprising:

obtaining topic corpus quality measures for other search topics that have topic search volumes that are within a threshold value of the topic search volume for the particular search topic; and

determining the threshold value based on the topic corpus quality measures for the other search topics.

18. The memory device of claim 13 , further comprising instructions that cause the one or more computers to perform operations comprising:

obtaining topic search volume values for other search topics that have topic corpus quality measures that are within a threshold value of the topic corpus quality measure for the particular search topic;

determining a threshold search volume value based on the search volume values for the other search topics;

determining that the topic search volume for the particular search topic exceeds the threshold search volume value; and

classifying the particular search topic as an underserved topic.