You can't afford a Kardashian, Christiano's people aren't answering your calls, and The Rock is busy standing in swimming pools holding puppies all week. Is your influencer campaign dead in the water? Not necessarily.

When it comes to influencer marketing you may assume that the bigger the name, the better the campaign. But it doesn't really work like that. Andy Warhol observed that in the age of mass media everyone would be famous for fifteen minutes. Fifty years later, social media means that everyone will be famous for 1500 people.

Micro-influencers, social media users with between ten thousand and a hundred thousand followers, can provide great value for money. Rather than paying a lot to reach millions of people in order to speak to a few thousand who are interested in your product, you can pay less to talk directly to those few thousand people through a channel they have chosen to follow due to their interest in your field.

The Rock's 82.5 million Instagram followers are fans of The Rock as a celebrity, as a wrestler, as an actor, or as a fitness inspiration. By comparison, the 16 200 Instagram users following South African sprinter Akani Simbine are following him because of their particular interest in athletics.

If you are promoting athletics gear, you will probably see a better conversion rate by partnering with Akani Simbine and ten or twenty other relevant local tastemakers than you would by partnering with The Rock. Because Simbine's audience has self-selected, you won't be paying to reach the 95% of The Rock's audience who have no interest in your product. Rather, you'll be reaching an audience entirely composed of people who want what you're selling.

Influencer marketing is not a radically new concept – successful Roman gladiators were lending their names and images to products two thousand years ago. Where it is innovative is in the influencer's ownership of the channels on which they are distributing their endorsement of your brand. This allows them to share their authentic experience of your brand with their followers.

Sitting in the sweet spot between celebrity endorsements and word of mouth, micro-influencer marketing gives brands the means to produce authentic, targeted, and persuasive content that audiences want to engage with.