9. A computer program product comprising a computer readable storage medium having a computer readable program stored therein, wherein the computer readable program, when executed on a data processing system implementing a Question and Answer (QA) system, causes the data processing system to: process, by the QA system, a first question to generate an answer to the first question and a supporting evidence passage that supports the answer to the first question being a correct answer to the first question; perform, by the QA system, a lookup operation in a question repository based on an identifier of the supporting evidence passage to identify an entry corresponding to a previously processed question, different than the first question, that previously had an answer generated based on the supporting evidence passage; return, by the QA system, the previously processed question and the answer to the first question to a submitter of the first question; calculate, by the QA system, an affinity score of the first question, wherein the affinity score represents an affinity between the first question and the supporting evidence passage; and store the first question and the affinity score in the question repository in association with the supporting evidence passage, wherein the computer readable program further causes the data processing system to calculate the affinity score of the first question at least by: clustering one or more topics in the first question; determining a correspondence of the supporting evidence passage to one or more clusters of the one or more topics in the first question; and calculating an affinity score based on the correspondence, wherein the affinity score is calculated to be relatively higher in response to the supporting evidence passage being clustered in the one or more clusters than in response to the supporting evidence passage not being clustered in the one or more clusters.
14. The computer program product of claim 9 , wherein the computer readable program further causes the data processing system to calculate the affinity score of the first question at least by calculating the affinity score of the first question based on one or more of a confidence score associated with the answer to the first question, term co-reference scoring, cosine similarity scoring, and clustering of documents.