Today President Obama will slip into Air Force One, wing over to Oslo and, once again, touch foreign soil.

Not so exceptional. To date, Obama has visited twenty countries as president, a travel pace that puts him ahead of any other president, as you’ve no doubt heard.

“That certainly gives insight into this president and his priorities, and what he’s up to,“ says Mark Knoller, CBS radio news’s veteran White House correspondent.

And he ought to know, since he’s keeping track—and has been for a long time.

“I started covering the White House in the end of the Ford campaign in ‘76. I covered Carter and Reagan for a few years each,” says Knoller. “Starting the last year of Bush 41, I’ve covered them all through now. Non-stop.”

But Knoller’s reputation for being a go-to facts and figures guy in the White House pool isn’t just because of his long service. It’s a necessity-is-the-mother-of-invention story dating back to the early years of Bill Clinton’s presidency.

“He was about to make a trip to California, and I said, ‘Gee, he’s been there a few times already. I wish I knew how many times he had been there,’” Knoller remembers. “And it took me forever to go back and put together those numbers. So I started keeping a record.”

“Back in those days, in the early nineties, the Internet was not fully up to speed. You’d go to Facts on File, but there wasn’t so much information readily available. So it was difficult, which is why I started to keeping it on my own,” says Knoller, who updates the document nearly every day. “It is ever much so more thorough and easy if I keep a contemporaneous record of everything the president does.”

So, since that trip, Knoller’s computer has been home to a variety of continually updated databases cataloging the sort of presidential arcana that one might assume would be someone else’s job—the White House travel office? An archivist? A think tank?—to track.

“I keep a daily log of everything the president does. I keep a list of speeches. I keep a list of travel—foreign travel, domestic travel. A list of outings. A list of golf. A list of pardons, vetoes, states that he’s visited, states that he hasn’t visited,” says Knoller. “Every time he goes on vacation, every visit to Camp David—things like that.”

In the last month Knoller has produced a CBSNews.com post noting Obama’s relatively sluggish pace of states visited as president, and fed information to The Wall Street Journal (showing that Obama has already golfed more to than his predecessor did in two terms), to Mike Allen’s widely read Politico “Playbook” (noting, on the day of Obama’s West Point speech, how rare it is for a president address the nation from outside the White House), and to The Washington Post (tallying the twenty-eight fundraisers the president has attended).

As that roll call would suggest, Knoller says he gets a lot of requests for the information, not just from fellow Washington reporters, but also from authors and academics. Despite that demand, and the obvious public interest, he has no plans to put the data online.

“I think my colleagues would say I’m pretty generous in sharing my information. I’ve never turned any of my colleagues down when they ask for stuff,” says Knoller. “I’d rather keep it, you know, in my proprietary.”

Clint Hendler is the managing editor of Mother Jones, and a former deputy editor of CJR.