The moguls were out in full frolic on Tuesday at Michael’s, the ego gymnasium of Manhattan media. Not only was Bill Clinton in the house, hosting some folks from his Global Summit, but so were Barry Diller of IAC/InterActiveCorp, Peter A. Chernin, formerly the president of the News Corporation, Jeffrey L. Bewkes, who runs Time Warner, and Edgar Bronfman Jr., head of the Warner Music Group.

By most accounts, it was smiles and hearty handshakes all around, and why not? They are a fun bunch with mystical reputations for lording it over not just huge media conglomerates, but American’s cultural consciousness, as well.

But their good mood has nothing to do with their ability to return value to their shareholders. A new book, which comes out Oct. 15, “The Curse of the Mogul: What’s Wrong With the World’s Leading Media Companies,” by Jonathan A. Knee, an investment banker and media professor, along with Bruce C. Greenwald and Ava Seave, maintains that in the aggregate since 2000, large media companies have written down $200 billion in value.

Gee, even at a time when billion seems like the new million, that seems like a lot of money.

“They convince people that there is something magical and special about managing the creative process,” Mr. Knee said over lunch. “Moguls are fun — they do mogul-y things like big deals and make grand pronouncements, but they are not usually a good thing when you stand back and look from a value perspective.”

“Curse of the Mogul” does a pretty good job of stepping back. From 1995 to 2005, the Walt Disney Company, Viacom, Time Warner and the News Corporation returned an average of 2.5 percent to shareholders while the Standard & Poor’s 500-stock index returned 9 percent, according to Mr. Knee’s book. And now that big media companies are under attack from a growing digital insurgency, their tendency to underperform the market has only grown.

At lunch last week at the Four Seasons (long on bankers, short on moguls), Mr. Knee maintained that the media chieftains continue to operate on principles that have lost salience, if they ever had any in the first place.

“The four pillars of media conventional wisdom have not changed: First, growth at all costs; second, content is king; third, the answer to all problems is to expand globally; and finally, that by embracing convergence and the Internet, they will be able to solve all their problems,” Mr. Knee said.

According to the book, there is indeed a correlation between unrestrained growth and value — an inverse one. Often, the faster the top line grows, the worse the bottom line does, in part because media companies are too impatient to sensibly build from within and instead make acquisitions at prices that are determined as a multiple of ego, not revenue.

“Time and again, moguls get frustrated with the margins in their own businesses and overpay for businesses they know nothing about,” Mr. Knee said.

So Rupert Murdoch gets a victory lap for buying MySpace but ends up casting about for revenue to justify the purchase.

And it’s hard to get in and out of this discussion without mentioning AOL-Time Warner, a nuclear corporate event that, according to Mr. Knee, will mean that when AOL is spun off, it will be worth about 1 percent of the market price that was assigned to it at the time of the merger.

“The fact that Gerry Levin was able to perpetrate this transaction precisely explains the problem with these businesses,” Mr. Knee, who is an investment banker at Evercore Partners and director of the media program at the Columbia Business School, said. “They shop because they can. No one will stop them.”

Convergence, he said, is just another way of describing the destruction of barriers to entry, a moat that gives those inside its perimeter a way to print money. After more than 100 digital business deals since 2000, Sony, Time Warner, NBC Universal, Disney, Viacom and the News Corporation have mostly written down digital efforts that have not panned out.

Some of the blame falls at the feet of those of us who walk around with notebooks. We love new, we love sexy, and we are all about the moguls and the grand pronouncements and tend not to worry so much about performance. While we were all riveted by watching mogul poster boy Jean-Marie Messier of Vivendi sacrifice a perfectly good French water utility on the altar of synergy, many other media companies stuck to their core businesses and returned value to their investors.

For example, the Meredith Corporation, a publishing company based in Des Moines, with titles like Ladies’ Home Journal and Better Homes and Gardens, achieved margins of around 17 percent in the 10 years ending in 2007.

But did you see any articles trumpeting Meredith’s performance from me or anybody else? We’re more prone to celebrate Ted Turner, who made millions on billboards, created a whole new television category with CNN, almost lost it all trying to re-create a movie company and then got battered around in the AOL-Time Warner merger before heading back to the ranch. Now that’s a story.

As someone who has covered MogulWorld off and on, I can tell you there is something hypnotic about it. A few years ago, I was in the Hollywood office of a studio executive for one of the conglomerates. He showed me a list of the 13 movies that they had for the year, and I had no trouble discerning which movies, give or take, would click and which would bomb — you wouldn’t, either. At the time, I thought, this is his only job — picking these movies — and yet, he was failing to see what was right in front of him.

I asked another executive higher up in the same media company about it, and he took the time to give me a head pat: “Movies get made for a variety of reasons, much of which have to do with maintaining relationships with A-list talent, so it may not be important that a specific movie makes money.” Gosh, this mogul stuff really is complicated.

Of course, a shift in the old ways of thinking — those four pillars — is under way. Talent is no longer bossing studios around, and deal flow has slowed to a trickle. Mr. Bewkes is busy making Time Warner smaller, not bigger, Mr. Chernin has moved on to a production deal of his own, and even Sumner Redstone is breaking up what he put together in the first place. So while the moguls still gather to frolic at Michael’s, the word “synergy” probably never comes up.