ROI for advertising is generally measured by local businesses in terms of phone calls generated, call duration and/or store visits. That isn’t changing soon. But for local ad sellers and their advertisers, it remains a challenge to figure out where calls are coming from; the conversion rate of calls; and the viability of Web-related tie-ins such as click to call and pay per call.

Few executives, if any, have more first-hand experience in these matters than Richard Rosen, who led development efforts at CallSource and more recently, at Jambo. Rosen, who just launched Calling Strategies, a consulting firm, says it is “inevitable” that there will be converging interests among the vested parties. These include local ad channels, like Yellow Pages and Newspapers; enhanced phone service providers, like Jambo, Ingenio, EStara, VoiceStar and MediaTraks; and the telecom providers that lease the lines.

Call tracking is highly desirable to both advertisers and publishers, says Rosen. But the economics of the issue will determine how it is done. Basically, “you have call measurement or pay-per-call,” he says. Call measurement requires an investment in dedicated phone numbers and some type of usage charge in order to prove ROI to an advertiser. Pay per call requires an entrepreneurial investment by providers in the phone lines in hopes of generating a premium “per call” fee to recoup those costs.