- Unlike paid search advertising, where one can focus on thousands of key phrases, natural search requires focusing on a small number of key phrases. Also, with paid search there is no charge unless someone actually clicks on an advertisement, the effort and cost of natural search is expended simply to have the website listing shown. Ideally, the effectiveness of particular key phrases has been measured via a properly configured and managed paid search campaign. This provides both Click Through Rate (CTR) and Conversion Rate (CR) data on a key phrase by key phrase basis. This data can be then married with various metrics indicating the relative competitiveness of key phrases, so that the most important key phrases can be chosen.