Whether it’s a sports star doing a commercial for Gatorade or a Kardashian showing off the latest brand of makeup, advertisers have long known that influencers drive purchases. If it’s cool for Lebron James to wear Nikes, then it’s cool for a 13-year-old kid to wear Nikes.

It seems simple enough, but ecommerce is changing in a big way. How do influencers affect purchases in today’s social-media driven landscape, and how can brands capitalize on influencers and their armies of social media followers?

Twitter reports that 40% of users say a Tweet from an influencer drove them to make a purchase. Meanwhile, 20% said an influencer drove them to share a product recommendation. The findings come from a recent study that Twitter conducted with research firm Annalect. Check out Twitter’s research here.

A few takeaways:

  1. Influencers are trusted just as much as friends: “When looking for product recommendations, 49% of respondents to our survey said they relied on influencers. That’s second only to Tweets from friends, who 56% of consumers sought for guidance,” says Twitter. “Furthermore, recommendations from influencers were amplified on Twitter, with 20% of subjects saying a Tweet from an influencer inspired them to share a product recommendation.”
  2. Influencers drive purchases: “Influencers on Twitter make your existing advertising efforts work even harder,” says Twitter. “Our research showed that those who were exposed to brand Tweets had a 2.7x lift in purchase intent over participants who did not see an advertiser Tweet. When participants were exposed to a campaign that featured both brand and influencer Tweets, the lift in purchase intent more than doubled to 5.2x.”
  3. Lots of people follow the brands themselves: “Not surprisingly, our study showed traditional influencers like actors, athletes and musicians continue to have the broadest reach among audiences,” says Twitter. “More than half of Twitter users follow actors and musicians. Perhaps less expected was the fact that people said a brand’s own product recommendation held significant influence over their decision.”

Harnessing the power of influencers is just one way to drive more purchases — especially from millennials, who will hold the bulk of the purchasing power by 2017. Want to learn more? Check out our guide Marketing to Millennials: Engaging a Generation of Millennial Buyers.

Adweek caught up with Jeffrey Graham, Twitter’s vice president of market research and insights, who says influencers can be an “ROI machine” for marketers.

“I think what this is telling us is that you don’t have to be a mass media star or a household name to be influential and actually drive people to buy stuff,” Graham told Adweek. “But actually, this whole cadre of influencers through social media—especially Twitter because that’s what we know about from the research—are driving a lot of purchases by a lot of people.”

Twitter is a great start for brands — it seems like they’ve been on the platform forever. But in an increasingly visual world, Instagram is key. Here’s what Instagram influencers have to say about sharing amazing content.