11. A method, comprising: receiving data indicative of search traffic directed to a website, the search traffic resulting from an unpaid portion of a search advertising campaign and a paid portion of the search advertising campaign; identifying a change made to the paid portion of the search advertising campaign; determining, with a computing device and based on the received data: a first volume of search traffic resulting from the unpaid portion before the change, a second volume of search traffic resulting from the unpaid portion after the change, a third volume of search traffic resulting from the paid portion before the change, and a fourth volume of search traffic resulting from the paid portion after the change; generating, with the computing device, a synergy score based upon the first volume, the second volume, the third volume and the fourth volume, wherein the synergy score quantifies an impact of the change on the search traffic resulting from the unpaid portion; and storing the synergy score in a storage medium in association with an indication of the change.
11. A method, comprising: receiving data indicative of search traffic directed to a website, the search traffic resulting from an unpaid portion of a search advertising campaign and a paid portion of the search advertising campaign; identifying a change made to the paid portion of the search advertising campaign; determining, with a computing device and based on the received data: a first volume of search traffic resulting from the unpaid portion before the change, a second volume of search traffic resulting from the unpaid portion after the change, a third volume of search traffic resulting from the paid portion before the change, and a fourth volume of search traffic resulting from the paid portion after the change; generating, with the computing device, a synergy score based upon the first volume, the second volume, the third volume and the fourth volume, wherein the synergy score quantifies an impact of the change on the search traffic resulting from the unpaid portion; and storing the synergy score in a storage medium in association with an indication of the change. 12. The method of claim 11 wherein the generating includes determining the synergy score based at least in part upon a relationship (R) comprising: 
 R =( TO 2 −TO 1)/( TP 2 −TP 1) wherein TO1 represents the first volume, TO2 represents the second volume, TP1 represents the third volume and TP2 represents the fourth volume.