Facebook and Twitter — they’re critical to your business, right? Um… no. In fact, the three biggest drivers of business online are 1) Web searches, 2) cost-per-click ads (think Google), and 3) e-mail.

That’s the finding from e-commerce analytics firm Custora, which looked at four years’ worth of online retail data to see what drove customers.

Facebook? Twitter? Useless. Here’s the chart ("CPC" means cost per click ads):

A graph showing how much more important Web searches and e-mail are

From a practical point of view, that means two things. First, make sure you’re findable on the Web — if someone looks for your name or simply "Realtor in [insert city name here]," you should show up.

Second, if you have clients’ e-mail addresses, use them. (Smartly, that is. Don’t spam.)

Big ol’ caveat: This research is looking at retail sales, which are obviously different thing than what you do. And it’s concerned with what kind of marketing brings is the most paying customers, which is why pay-per-click ads are so high — someone who clicks an ad is probably in the market to buy something.

Still, the core of the research is valuable. For all the chatter about having a Facebook presence and a Twitter feed, those don’t seem to be all that useful from a business standpoint. (But they’re great for learning what Aunt Bee had for lunch.)

Read more over at Wired.