In a wide-ranging interview Thursday on the How Leaders Lead podcast with host David Novak, the head of the second largest U.S. oil company by market cap explained how recognizing others is an important piece of maintaining a strong corporate culture.

For example, when he visits Chevron employees around the world, they serve as his hosts, show him their operations, and take him to meet customers.

Afterward, he writes a letter to them—the “old-school, on paper” kind that you don’t get much anymore, Wirth pointed out.

He added that he pays careful attention to each person he interacts with and sends letters to each one to thank them for their time as well as recognizing what they talked about and sharing how much he valued it.

“I think back to when I was early in my career, and if a CEO had sent me a letter and actually knew what I was doing, it would have been a really big deal for me,” Wirth said. “And so I try to remember what it was like to be in the jobs that I’m visiting and that I had those jobs myself one time. And I want to make sure that people know that I appreciate them.”

When you’re running a company as big as Chevron, all those meet-and-greets can add up. After coming back from a trip, Wirth estimated that he writes 60 to 80 letters.

“It’s important to me that I make sure people understand that I was paying attention and I really do value what they do,” he explained.

Taking the time to write thank-you letters can pay off as recent surveys show many workers don’t feel valued enough.

According to a report from Canva, 56% feel appreciated or very appreciated at work, while 44% feel unacknowledged or neutral in how their employer addresses their contributions, and 75% wish they felt more valued.  

Meanwhile, other CEOs also go out of their way to show their appreciation with personalized notes.

Neiman Marcus CEO Geoffroy van Raemdonck swears by them and told Fortune last year that he sends thank-you notes every single day.

Before the COVID-19 pandemic, van Raemdonck said he would send anywhere between three and five handwritten thank-you notes a day. During and after the pandemic, as workers switched to remote or hybrid work schedules, he switched to texts, emails, and quick phone calls. 

“I want to be a generous leader,” he said. “The way I remind myself is by recognizing the generosity of others.”