BURBANK, CALIFORNIA - OCTOBER 29: Robert Greenblatt, Chairman of WarnerMedia Entertainment & Direct-To-Consumer, speaks onstage at HBO Max WarnerMedia Investor Day Presentation at Warner Bros. Studios on October 29, 2019 in Burbank, California. (Photo by Presley Ann/Getty Images for WarnerMedia)
PHOTO: Presley Ann/Getty Images for WarnerMedia
BURBANK, CALIFORNIA - OCTOBER 29: Robert Greenblatt, Chairman of WarnerMedia Entertainment & Direct-To-Consumer, speaks onstage at HBO Max WarnerMedia Investor Day Presentation at Warner Bros. Studios on October 29, 2019 in Burbank, California. (Photo by Presley Ann/Getty Images for WarnerMedia)
Now playing
02:15
Here's a first look at the new HBO Max
PHOTO: CNN
Now playing
03:39
YouTube CEO on election misinformation and QAnon
PHOTO: Shutterstock
Now playing
05:18
3M CEO: Meeting demand for N95 masks is still a challenge
LOS ANGELES, CA - NOVEMBER 17:  Airbnb CEO Brian Chesky speaks onstage during "Introducing Trips" Reveal at Airbnb Open LA on November 17, 2016 in Los Angeles, California.  (Photo by Mike Windle/Getty Images for Airbnb)
PHOTO: Mike Windle/Getty Images North America
LOS ANGELES, CA - NOVEMBER 17: Airbnb CEO Brian Chesky speaks onstage during "Introducing Trips" Reveal at Airbnb Open LA on November 17, 2016 in Los Angeles, California. (Photo by Mike Windle/Getty Images for Airbnb)
Now playing
03:29
Airbnb CEO: The travel industry is more resilient than anyone thought
MANCHESTER, NH - FEBRUARY 8: Republican Presidential candidate Carly Fiorina holds "Coffee With Carly" at Blake's Restaurant February 8, 2016 in Manchester, New Hampshire. (Photo by Darren McCollester/Getty Images)
PHOTO: Darren McCollester/Getty Images
MANCHESTER, NH - FEBRUARY 8: Republican Presidential candidate Carly Fiorina holds "Coffee With Carly" at Blake's Restaurant February 8, 2016 in Manchester, New Hampshire. (Photo by Darren McCollester/Getty Images)
Now playing
03:17
She was a trailblazing CEO. Then fired. Why Carly Fiorina doesn't regret it
Now playing
03:06
She went from high school dropout to SF Fed president
Now playing
03:28
Marc Benioff: Capitalism is dead
PHOTO: CNN
Now playing
03:50
Microsoft President: There is a privacy crisis
PHOTO: Angela Weiss/Getty Images
Now playing
03:09
Winklevoss twins on crypto: Wall Street has been asleep at the wheel
PHOTO: Ari Perilstein/Getty Images North America
Now playing
03:14
SoulCycle CEO on the Peloton threat
Google CEO Sundar Pichai poses for a portrait at the Mayes County Google Data Center in Pryor, Oklahoma, June 13, 2019. Nick Oxford for CNN
PHOTO: Nick Oxford for CNN
Google CEO Sundar Pichai poses for a portrait at the Mayes County Google Data Center in Pryor, Oklahoma, June 13, 2019. Nick Oxford for CNN
Now playing
03:32
Sundar Pichai: I never asked to be Google CEO
NEW YORK, NEW YORK - FEBRUARY 05: Melinda Gates speaks onstage at Oprah's SuperSoul Conversations at PlayStation Theater on February 05, 2019 in New York City. (Photo by Bryan Bedder/Getty Images for THR)
PHOTO: Bryan Bedder/Getty Images for THR
NEW YORK, NEW YORK - FEBRUARY 05: Melinda Gates speaks onstage at Oprah's SuperSoul Conversations at PlayStation Theater on February 05, 2019 in New York City. (Photo by Bryan Bedder/Getty Images for THR)
Now playing
01:41
Melinda Gates calls for paid family leave
Now playing
02:58
Weight Watchers CEO says it will survive the Keto craze
RANCHO PALOS VERDES, CA - FEBRUARY 07:  Executive Editor, Recode Kara Swisher attends The 2017 MAKERS Conference Day 2 at Terranea Resort on February 7, 2017 in Rancho Palos Verdes, California.  (Photo by Emma McIntyre/Getty Images for AOL)
PHOTO: Emma McIntyre/Getty Images North America/Getty Images for AOL
RANCHO PALOS VERDES, CA - FEBRUARY 07: Executive Editor, Recode Kara Swisher attends The 2017 MAKERS Conference Day 2 at Terranea Resort on February 7, 2017 in Rancho Palos Verdes, California. (Photo by Emma McIntyre/Getty Images for AOL)
Now playing
03:14
Kara Swisher: Tech companies need ethics officers with power
CULVER CITY, CA - JUNE 09:  Gwyneth Paltrow speaks onstage at the In goop Health Summit at 3Labs on June 9, 2018 in Culver City, California.  (Photo by Neilson Barnard/Getty Images for goop)
PHOTO: Getty Images
CULVER CITY, CA - JUNE 09: Gwyneth Paltrow speaks onstage at the In goop Health Summit at 3Labs on June 9, 2018 in Culver City, California. (Photo by Neilson Barnard/Getty Images for goop)
Now playing
02:51
Why Gwyneth Paltrow feels like an impostor CEO

AT&T said this week that it would split the role of board chair and chief executive when its current chairman and CEO Randall Stephenson steps down.

The move will put AT&T, which owns CNN’s parent company WarnerMedia, among a majority of large, publicly traded US companies that are now opting to keep those two roles separate.

“The trend toward separating the roles has been growing steadily for more than a decade,” a 2019 report from executive search firm Spencer Stuart noted.

Today, 53% of S&P 500 companies do so, up from just 30% in 2005, according to data from Institutional Shareholder Services.

There is still plenty of debate over the best way to structure boards. But there has been a growing belief – particularly among institutional and activist investors – that the more independent the leadership of a board, the better.

A corporate board, after all, is charged with the hiring, firing and oversight of CEOs and planning for a company’s future.

Activist shareholder Elliott Management, for instance, called for a separation of the board chair and CEO roles at AT&T, although AT&T said it had already been planning the move.

In surveying institutional investors this year, ISS found that while some strongly believe it’s important to keep the chairman and chief executive roles separate, others can live with a combined chair/CEO role so long as there is also a strong lead independent director appointed.

CalPERS, for instance, which invests on behalf of California’s public employees, most strongly favors a separation of roles except in very limited circumstances, whereas mutual fund giant BlackRock falls into the second group.

ISS also asked investors what reasons would “most strongly suggest” the need to separate the roles. The top three were poor responsiveness to shareholder concerns, practices that weaken or reduce board accountability (e.g. not permitting shareholders to call a special meeting), and a corporate crisis such as a product failure.

That seems to be what happened at Boeing. After two deadly Boeing 737 Max crashes, a protracted grounding of those jets and a major report faulting Boeing and the FAA for failure in certification of the 737 Max, CEO Dennis Muilenburg was stripped of his chairmanship.

Do companies do better when the roles are separate?

It certainly sounds reasonable that a board – and by extension its chair – should be independent from the top management of the company to better assess things objectively.

But some governance experts don’t think it’s as cut and dry as that.

A lot of research on the issue reviewed by the Rock Center for Corporate Governance at Stanford University, for instance, found no correlation between board chair status and company performance, and in some cases no impact on organizational risk taking and executive pay practices either.

“There are no doubt situations where it makes sense to separate the two positions – maybe complex turnarounds or dealing with governance problems. However, this does not mean every company should separate the roles. There is context to this decision,” said Rock Center director David Larcker.

For instance, “there are a lot of efficiencies to having a capable, honest and knowledgeable person serve as leader of both management and the board,” said Larcker’s Rock Center colleague Brian Tayan, a Stanford Law School researcher.

And what if the roles are separate but the CEO and the chair are close friends?

“Is that really better?” said Larcker.