How DO You Count Those Passengers?

I was having a conversation with a friend recently that’s interviewing with Google.  He told me that as part of the interview they asked him a couple of seemingly random questions to understand his problem-solving capabilities.

I asked him what his answers were to the questions they asked and he said the answers were irrelevant.  One of the questions he was asked related to the world of travel, so I reminded him that nothing in the travel world is really that irrelevant to me.  The question was:

How may people do you think travel through SFO airport every day?

Turns out, it wasn’t irrelevant.  And, it turns out SFO has an interesting way of counting people.  My friend told me that the answer was something like 40MM+ a year.  That really didn’t sound right to me, but he was pretty insistent he had found info on SFO’s website asserting that claim (as in, over 30MM people YTD).  I recalled the number being much lower.

I double-checked the FAA numbers and, sure enough, SFO was the 7th biggest airport by number of enplanements.

When I showed him those numbers, he pointed me to SFO’s info.  Sure enough, they listed over 30MM passengers thus far.  But, if you read the footnotes, you’ll see that their count of total passengers includes both enplanements and deplanements.  So, a passenger getting off on one plane and onto another counts twice.

I wouldn’t choose to call that “Total Airport Passengers”, but hey.

Google, you may want to pick a different question.


  1. I guessed 100,000 per day (100 gates x 200 passengers per flight x 5 times per day). That’s 36.5MM per year, so a pretty good guess…hey, Google, hire me!

      1. Since the question asks for how many people travel through SFO per day, I’d say you can’t count the same person twice in answering that specific question. However, I think SFO’s way of counting is designed not to identify individual separate people, but total traffic they serve. It’s logical that a person who both gets on and off an airplane will count twice in their statistics, as opposed to, say, someone who arrives in San Francisco by air and leaves by some other method.

        1. Dave, I just don’t see it that way. Other than two jetbridges, I would think a connecting passenger using less services then a departing or arriving passenger (baggage claim, roads leading to the airport, etc). I think the FAA enplanement stat is the standard here.

  2. SFO’s not alone in fudging its number that way. It annoys me to no end when I read reports that an event like a festival gets X hundred thousand visitors when that number counts the same people every time they attend one of the events, often with the same person attending several events, thus being counted multiple times. I suppose the SFO number would be correct if it was measuring passenger movements, but I tend to agree with you, it hardly seems right.

    1. DavidB, I’m sure they’re not alone fudging it. And, really the only reason it caught me off guard was because I roughly recall how many passengers ATL moves on a yearly basis, and that SFO isn’t that close. But, hey, if it makes them feel better…..

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