Marketers were asked how likely they were to recommend a particular product or service. The aggregate rating for ad agencies was 21%, meaning that very few clients would recommend their agencies' services to others.

The flip side is that 76% of marketers had no way to determine their ROI from their lead agencies, and 69% said ROI is too difficult to measure.

"There's always an undercurrent of discontent with agencies," said Peter Kim of Forrester. "They're dissatisfied, yet on what basis? It's not because the agency didn't help them drive sales or meet some other business outcome. It's a vague disenchantment, or disappointment; it's a feeling that there isn't data to back up."

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