Marketers put their faith in gross rating points to determine their radio advertising. But advertising guru Roy H. Williams believes that measure can be terribly misleading, and explains why on his Monday Morning Memo website.
He notes that 100 gross rating points is the mathematical equivalent of reaching 100 per cent of the population of an area, one time each. But you can get the same number of gross rating points – and theoretically the same effectiveness – by reaching 50 per cent of the population twice; 25 per cent, four times; 10 per cent, 10 times; or 1 per cent of the population 100 times.
Repetition in advertising is what leads to sales, so these different possibilities are not equally effective even if they seem to be. He insists the average radio ad needs to be heard by the same listener at least three times within seven nights’ sleep – week after week after week. “Don’t skip weeks. Sleep erases advertising,” he warns. The longer the product purchase cycle for your offering – the time it takes people to decide – the longer your weekly radio schedule will need to run before you start getting your maximum return on investment.
Given a limited budget, you might need to reach out to fewer people but expose them to more ads. “The math that underlies the calculation of gross ratings points virtually guarantees your radio ads will reach too many people with too little repetition,” he writes.