Way back, it was relatively simple. The earliest forms of advertising, for example "Horse for Sale", could be judged very simply.
However, life is far more complicated than that now and a whole research industry has grown up around advertising to try to quantify return on investment.
One of those studies, Marketing in the Era of Accountability by Les Binet and Peter Field, released by the IPA last year, examined more than 800 IPA Effectiveness Awards papers.
One of the main findings of the study was that campaigns that have the objective of driving fame for a brand consistently outperform the average on most business metrics, including sales.
In a world where driving fame for a brand is a useful objective, it is pertinent to take a look at the techniques of a related field - the world of the publicists. Mark Borkowski's new book, The Fame Formula, takes an entertaining look at the creation and evolution of the publicity industry.
He starts with the kinds of techniques that were used in the early days of Hollywood in the 1900s - back then, the PR industry was more overt about chasing fame than the world of advertising.
Among many laugh-out-loud moments in the book (modesty prevents me from recounting the story of the appropriately named Tara Tiplady, but you shouldn't miss it), Borkowski shows how the world of publicity has changed from a controllable situation to one where fame is in the hands of the "punters".
Powered by the internet, everyone in today's world has the tools to "shape a star's success or comment on someone's failure".
Borkowski delivers a "fame formula", which asserts that there is a 15-month cycle to fame for most celebrities and brands, and that you need to refresh and renew your publicity in that period in order to keep the celebrity factor running.
While there are, of course, significant differences between driving fame for a celebrity and sustaining a successful brand long term, there are aspects of the techniques of publicists (the less outrageous ones that is) that might give you ideas.
Overall, I'd like to believe in Borkowski's opening statement: "For better or for worse, those who seek notoriety, whether it's a brand or personality, get the publicity they deserve, a prefabricated heaven or inescapable hell."
Sue Unerman is chief strategy officer at MediaCom, sue.unerman@haymarket.com