1. A computer-implemented method for dynamically reranking search results based upon source authority, the computer-implemented method comprising performing computer-implemented operations for: analyzing a received search query to determine a query topic associated with the search query; searching an authority index to identify authoritative sources relating to the query topic, the authority index comprising a plurality of entries, wherein each entry defines an authoritative source for content relating to the query topic, wherein identifying the authoritative sources comprises: accessing an authority index; searching the authority index for entries associated with the query topic; identifying a plurality of entries associated with the query topic, each of the plurality of entries being associated with a source having a corresponding authority value and corresponding to one of the promoted results, and defining the authoritative sources as the sources that authored the promoted results; obtaining, from the authority index, promoted results identifying the content relating to the query topic; computing at least one contribution dimension for the sources associated with the promoted results; generating a contribution dimension filter for filtering the promoted results and the search result based upon the contribution dimension; and dynamically reranking the promoted results and the search result based upon the contribution dimension in response to receiving input indicating a command to apply the contribution dimension filter to the promoted results and the search result; and outputting the reranked promoted results with the search result.