Search Engine Marketing firm iProspect has released a study they did that examines how offline marketing (which is the internet marketers euphemism for print, tv, radio)channels influence online search. The study found that magazine and newspaper ads (as well ad word of mouth) where the most effective at generating a purchase:

With the possible exception of the physical store channel – which one could theoretically browse from the hour it opened to the hour it closed and yet not necessarily be exposed to proactive “messaging” – the magazine/newspaper (print) ads channel, and the word of mouth channel, have the advantage of “time” in their favor. Unlike a television or radio ad that is viewed or heard over a 30-60 second period and is then irretrievable by the viewer/listener, and unlike the billboard or outdoor or transportation channels that pass by as quickly as the vehicle is moving, messaging from print ads and word of mouth can be extended in time.

A potential customer can hold and read a print ad again and again and again. It can be “studied” and retrieved again and again. And as highlighted earlier in this study, the indefinite duration, level of inherent trust, and highly interactive nature of the word of mouth channel are discussed as reasons that its messaging is of higher quality than all of the other channels.

It’s iProspect’s belief that these inherent advantages that the print channel and word of mouth channel have over the other channels addressed in this study cause them to produce more interested, more motivated searchers who are farther down the attention, interest, desire, action path at the point at which they launch their first search than individuals who have been exposed to other channels. The implication of this finding is somewhat obvious – when possible and appropriate, utilize these two channels in a coordinated and consistent fashion with both organic and paid search campaigns.

The iProspect Offline Channel Influence on Online Search Behavior Study can be downloaded for free on iProspect's Website.