Influencer marketing is a powerful tactic that targets consumers where they already spend much of their time: social media. Globally speaking, Instagram is the primary platform for many influencer-brand campaigns, but it's hardly the only one.

Take China, for example. Most of the major international social networks, including Facebook, Instagram, Snapchat and YouTube, are banned by the government. That means that the country's influencers hold court on local services, of which Weibo and WeChat are the most popular.

And in the DACH region—which includes Austria, Germany and Switzerland—Instagram and YouTube are neck and neck, at least in terms of influencer marketing spending. According to Goldmedia data, sponsored content on the two platforms accounted for 34% and 31% of total influencer revenues in 2017, respectively.

Spending figures don't always tell the whole story. While Goldmedia took into account both monetary and nonmonetary compensation, such as product gifting, influencers may charge a premium for a post on a certain platform, which could inflate its share of spending.

But those findings make sense when looking at where consumers in the region follow influencers. According to a March 2018 survey by M Science for Wavemaker, social media users in Germany were just as likely to follow an influencer on YouTube as they were Instagram, each cited by 73% of respondents. Roughly half said they followed influencers on Facebook.

That said, the importance of Instagram for influencer campaigns is rising in nearly every market worldwide.

In a February 2018 survey by influencer marketing agency Activate, 88.9% of worldwide influencers said they were using Instagram for influencer marketing campaigns more than they did one year ago. Excluding posts on their feeds, Instagram Stories was the most popular tactic used for sponsored campaigns.

Instagram's rising popularity for influencer campaigns goes hand in hand with the platform's strong user growth, as marketers tend to go where their customers are.

India is one example of that. According to our latest forecast, the number of Instagram users in the country grew by an explosive 123% in 2017—the fastest growth rate worldwide. So it's no surprise that 78% of influencers in India cited Instagram as the platform that would rise in importance for influencer marketing this year, according to a December 2017 survey from influencer marketing agency Buzzoka.

Overall, we expect the number of worldwide Instagram users to rise by 18.4% to 714.4 million in 2018. Sweden will have the highest Instagram user penetration rate in the world, at 68.9% of social network users, followed by Indonesia (62.8%) and Norway (57.7%).

In the latest episode of "Behind the Numbers," eMarketer's Jasmine Enberg and Debra Aho Williamson provide an overview of the global state of influencer marketing, including spending, top platforms and the role of influencers in the path to purchase. "Behind the Numbers" is sponsored by Mower.