SAUSALITO, Calif. — When someone buys something online today, it’s not easy to figure out how they ended up making their purchasing decision. That’s why the most important thing marketers can understand is the path a customer took to that decision.

That was the overriding message from Google vice president of performance media Jason Spero. Speaking in this town just across the Golden Gate Bridge from San Francisco, Spero made it clear to a packed room at VentureBeat’s Mobile Summit that we no longer live in a world where people can be counted on to buy things after encountering them on a single device.

Instead, Spero said, people’s purchases increasingly come after a journey across two or even three (or more) devices. And understanding that path is key to success.

“The more you can capture data” about that path, Spero said, “the more you can have a one-to-one conversation” with the consumer.

Added Spero, the more data you capture about the consumer’s consideration of a product, “the more you can build attribution models for a multi-touch world,” he said, referring the tying of purchases to mobile marketing content.

Spero also noted that one of the most important conversations marketers can have these days is about who is doing a good job of engaging consumers. “It’s going to be about who has the data,” he said, and “who understands that user.”

Ultimately, he said, it doesn’t matter what other kind of data you add to the mix as you try to understand a consumer’s purchasing behavior as long as you start by knowing their intent. Everything else, Spero said, “layers on intent.”

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