The truth about Merger Monday

The rumors of Merger Monday's death have been greatly exaggerated.

A number of recent news reports have heralded the end of the beginning of the week tradition of Wall Streeters holding their M&A announcements for Monday morning, hoping for a full week of positive press following the announcement. Some have suggested it's now merger Tuesday or even merger Thursday. The Big Crunch dug up some data to check those assertions.

It turns out that Merger Monday is alive and well, at least for the deals that really matter. (One news outlet's analysis looked at thousands of smaller deals, not the kind of thing that would make front page news. And another outlet's analysis said that half the deals happened on days other than Monday. That's the same thing as saying Monday has as many deals as every other day combined.)

We looked at announcements of U.S. M&A deals valued at more than $1 billion since 1995. So far in 2015, 33 percent of deals were announced on a Monday, down from 2014's 37 percent, but on par with recent years.

For a sample, look at Warren Buffett's recent Monday announcement of Berkshire Hathaway's purchase of Precision Castparts for $235 a share. Not only was that 21 percent above the previous day's closing, but it was one of the biggest deals Buffett has made as head of Berkshire and the sixth-largest U.S. M&A deal this year.

The deal demonstrated the Oracle of Omaha's faith in the aerospace sector and lends credence to the idea that Merger Monday is still around. After all, the deal had been in talks for weeks before the announcement, Buffett told CNBC's "Squawk Box" recently.

There is one good statistical reason for why Monday is the most common day for M&A announcements: Banking pros don't take a day off.

Neil Dhar, partner in the deals practice at professional services firm PwC, said he's noticed the Merger Monday phenomenon and he thinks it is a simple matter of Wall Street's 24/7 hum of activity.

"I think a lot of those things are attributable to people working through the weekend," he said. It makes sense: If accountants and interns spend their Saturdays working on deals, then of course they'll come out on Monday morning. As a result, many M&A reports have now shifted their schedules from a Monday-Friday workweek to one that runs Sunday-Thursday, allowing them to be ready to jump on deal announcements when all other slackers get to work on Monday.

If bankers iron out details anytime between Friday afternoon and Sunday night, the first reasonable available time to announce is Monday. If you assume bankers work seven days a week, then those two full days (Saturday and Sunday) add 29 percent to the value of Monday over any other weekday.

That's pretty much what we find in the data, provided to CNBC by Dealogic: Between 1995 and July of this year, 36 percent of deals were announced on Mondays, followed by Tuesday with 19 percent.

Sure, some huge deals this year were not announced on Monday. The biggest, Charter Communications' $79.6 billion big for Time Warner Cable in May was announced on a Tuesday. But that was May 26, the day after Memorial Day.

M&A activity around the world has been at next-to-record levels all year. There were more than $2.3 trillion worth of deals in the first half of the year, according to Dealogic. That's second in half-year total value only to 2007, when there were $2.6 trillion announced.

Dhar said his team has been working like mad trying to keep up. "The last couple of years, M&A has been pretty robust," Dhar said. "U.S. CEOs have had a lot more confidence with the economy."

Strategy behind scheduling an M&A announcement usually has more to do with other corporate calendar events, Dhar said. He listed quarterly earnings announcements, avoiding conflicts with product launches and getting ahead of a leak. "It's more those types of things."

Even though it seems quiet on this slow August Monday, it turns out this is not even the quietest month for deals. Dealogic's data shows that January and March each had fewer M&A deals announced, making August only the third-slowest month of the year. It turns out that companies slow down with the cold weather: Under 7 percent of deals since 1995 were announced in January.