Why do adspend estimates differ?
Andrew GreenZenithOptimedia
According to Advertising Age, General Motors Corporation was the largest advertiser in the United States in 20041, spending just short of $4 billion. This estimate - made by the magazine – comprises spending in twenty 'monitored' media (e.g. television, radio, newspapers etc) alongside what are termed 'unmeasured' media (such as sales promotion, direct mail, couponing, co-op spending and so on). The report states that the unmeasured figures are estimates based on the difference between individual companies' 'reported or estimated ad costs' and the monitored figures provided by research...