No, this is not in recognition of those who have risked their lives in defense of our nation -- though they clearly deserve to be recognized and honored for what they've done. This column is written in acknowledgement of those who have dedicated their lives in defense of our nation's most powerful medium: television. Their weapons of choice were not rifles, grenades, or mortar fire. They were pocketpieces, meters and some analytical firepower. But they fought some important battles nonetheless, and their departure is as symbolic of the changes taking place in television as anything else.

The most recent to depart is Tim Brooks, the long-time research chief at Lifetime Television, who has spent a lifetime keeping the TV ratings business honest. Brooks hasn't actually departed yet, but he's announced that he'll retire at the end of this year, marking an end to a 30-year career that spanned NBC, USA Networks, and NW Ayer. Along the way, he has played key roles on industry oversight committees and councils that have set standards, policies and guidelines that have kept the business of TV ratings fair, balanced and as accurate as they possibly could. Brooks was always the voice of reason, and usually one of calm, during even the most contentious industry debates. And despite his devotion to numbers crunching, he somehow found time to serve as the industry's de facto historian, author of the definitive reference book on the subject: The Complete Directory to Prime Time Network and Cable TV Shows.

Brooks is not alone. At least two other longtime TV numbers-keepers - Turner Broadcasting's Michael Propper and Time Warner's Phyllis Liebert -- also retired this year, and some other important industry voices such as Knowledge Networks/Statistical Research Inc.'s Gale Metzger, have simply grown quiet. And I find it telling that the most dynamic voice in the TV ratings business in the past year has come from an outsider -- erinMedia's Frank Maggio, now an occasional contributor to this board -- who has been both brave and brash enough to take on Nielsen when so many have failed before him.

The real danger, KN/SRI's Metzger tells me, is the loss of "institutional" history about the TV ratings business, "and the knowledge of all the errors we made in the past and the risk of reliving them again."

Metzger, no big fan of the current direction of the TV ratings business -- and especially of a Nielsen Co. controlled by private equity firms more interested in cash flow and profits than research quality -- says he actually fears current trends will push people in the direction of more proprietary research.

"If I were the head of a major advertiser spending a lot of money on television, I'd invest more of my money on custom research, and rely less on syndicated research," he says. "If you're going to invest $100 million in advertising, you have to allocate something to realistically understand what you're getting for that."

But this column is not about the partisan issues surrounding the TV ratings wars. It is about the people like Metzger and Brooks who fought those battles with conviction, with purpose and with a great sense of moral consciousness.

Some have literally passed on recently, including long-time Nielsen chief statistician Ed Schillmoeller. Others, like Brooks, have retired. Still others have simply left the business, like Madison Avenue's Joanne Burke, Mary Ellen Vincent and Stacey Lynn Schulman, or have moved into research vendor roles like David Marans and Jon Swallen.

I'm not saying there aren't still vital voices on the TV ratings front. CBS' Dave Poltrack and NBC Universal's Alan Wurtzel are as vocal as ever, as is Turner's Jack Wakshlag. It's just that the debate seems to be losing some of its resonance as the chorus begins to dwindle. So I find the timing of Brooks' retirement symbolic. It comes as both TV measurement methods, as well as the medium itself, are undergoing radical change. So maybe, just maybe, an entire era of TV audience measurement has passed on, and we've just been too preoccupied to notice, as Brooks might suggest, its final episode.

"Whether it's 'Gunsmoke,' 'Dallas' or 'Everybody Loves Raymond,' even the longest-running television series eventually comes to an end, as does this phase of my work in television," Brooks said when announcing his retirement earlier this week.

While he plans to keep writing about the medium, we'll miss his whining about the medium behind-the-scenes.

So please take a moment this weekend to reflect on those brave men and women who've fought hard to be the conscience of a medium. And if I've left any important names out of this entry, please add them in your comments to the Board.

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