Over the years academics and analysts have attempted to show the value of brands (their ‘brand equity’) in terms both theoretical and monetary.

The Millward Brown BrandZ Top 100 report showed Apple to be the most valuable brand in 2013, with brand equity worth over $185bn; the other four top brands were, in order, Google, IBM, McDonald’s and Coca-Cola.

Since 2006 the BrandZ Top 100 has appreciated about twice as fast as the S&P 500.

Now J.K. Rowling, author of the “Harry Potter” series (as if anyone needed to be told), has inadvertently revealed the value of her brand.

In the spring Rowling released a new novel, ‘The Cuckoo’s Calling’. But she did it under the pseudonym ‘Robert Galbraith’. The description of the author on the book even acknowledged that this is a pseudonym. 

And the book was lavishly praised by reviewers:

Combines a complex and compelling sleuth and an equally well-formed and unlikely assistant with a baffling crime…A stellar debut.” (Publishers Weekly, starred review)

Cormoran Strike is an amazing creation and I can’t wait for his next outing. Strike is so instantly compelling that it’s hard to believe this is a debut novel. I hope there are plenty more Cormoran Strike adventures to come. A beautifully written debut novel introducing one of the most unique and compelling detectives I’ve come across in years.” (Mark Billingham, author of The Demands)

A remarkably assured debut. Robert Galbraith’s portrayal of celebrity-obsessed modern London is at once beautifully written and utterly engrossing, his characters so real you could eat dinner with them, his ever-coiling plot guaranteed to keep you up past your bedtime. I couldn’t put it down.” (Owen Laukkanen, author of The Professionals)

Some even said it was so good that they didn’t believe that it could be a first book. “This book is so well written that I suspect that some years down the road we will hear the author’s name is a pseudonym of some famous writer,” wrote one Amazon reviewer before Rowling’s identity was revealed.

But, despite the praise, the book had only modest sales, confirming for one editor who rejected it just how hard it is to launch a new author.

As soon as it was revealed last weekend by The Sunday Times that “Robert Galbraith” is, in fact, J.K. Rowling, though, sales immediately soared.

Given their small base, sales increased over 500,000% in just a couple days and the book shot to the top of the Amazon best-seller list. (NB: See this for Amazon’s ‘percentage trick’)

All because of J.K. Rowling’s brand equity.

Last year the value of her brand equity was proved in opposite fashion when she released her first non-Potter novel, “The Casual Vacancy”, under her real name. That book had mixed reviews, but had very strong sales from the moment it was available.

Some artists, of course, have followings who want to see whatever they create next, no matter what it is. It’s sort of as if the fans are having a conversation with the artist and buying the new work is their way of keeping up their end of the chat.

Kevin Kelly has said artists can make a very good living if they have just 1,000 true fans.  Rowling has orders of magnitude more fans, which is why she became one of the wealthiest people in the world, although her fortune has declined somewhat recently due to generous charitable donations (good for her).

And just as her fans will buy anything that she writes, Apple “fan boys” will buy virtually anything that the company puts out, Google users flock to its newest service, and people continue to believe that “no one was ever fired for choosing IBM”.

Brand equity is one of the factors that will always make marketing so complex and challenging, because what works for one brand doesn’t work for another. And now we have one more data point of just how valuable building your brand equity can be.