Influencer marketing has taken off in a big way during 2017. However,  according to new research published by Rakuten Marketing, the practice of hiring well-known celebrities and other individuals to promote products and services has not been without its drawbacks for brands that are finding it difficult to determine ROI and key metrics for their endeavours.

It is no surprise to see marketers turn to influencers en masse, as it effectively allows them to sidestep the challenges associated with building a target audience quickly. A popular social media personality, for example, already has a huge following, so it’s just a matter of placing the content in the right place at the right time to drive reach and awareness and engage with users.

However, while the potential benefits are enticing, more than a third of marketers have admitted they are not exactly sure the effect influencers are having on their brand due to an inability to effectively measure return on investment. This imprecision is particularly troublesome in a world where transparent, precise measurements are required to inform all types of decision making in marketing effectively.

“No one really quite knows what the best route to measure the impact of influencer marketing is,” said Michelle Stoodley, Benefit’s head of digital marketing. “It’s probably the only thing in digital marketing that exploded before there’s been any real benchmark for success. It kind of goes against a lot of what digital marketing is normally about, which is numbers, data and tracking.”

A separate study published by Rakuten Marketing and Moran Consulting in August found influencer marketing costs are rising in the UK. Posts by a celebrity with a social media following of more than one million now command a colossal £65,000 fee, though some premium fashion brands are paying more £160,000 per post for certain big-name influencers. In contrast, “micro influencers” with less than 10,000 followers average a relatively more palatable £1,350 per post.

In addition to worries about a hike in costs, brands could also be exposing themselves to additional risks. Marketing agency Mediakix revealed earlier in the summer that there had been several cases of brands striking deals with fake accounts on Instagram. The practice is also still very much in its infancy compared to other forms of digital marketing.

Despite concerns, influencer marketing is here to stay for now and is likely to command large percentages of brands’ budgets. The Rakuten Marketing study found three quarters are planning to spend more on influencers during the next twelve months. However, Stoodley urged brands to continue investing in other content formats to build reliable and flexible campaigns that can drive ROI in the long term.

She concluded: “Influencer marketing is probably the part of the digital marketing world that has the least amount of measurement and reliability, so to put all your eggs in one basket would be quite risky. Also, who knows where this part of the industry is going as brands start to pay influencers more and more? It can only go so far.”