We've heard it so many times:

"Oh it's okay, they won't know I've overstayed because there is no exit control when you leave the US"

"They don't know how long I've been out of the country, so I haven't abandoned my status"

This myth must die. Just because nobody stands in a booth marked "passport control" stamping passports as you exit the country does not mean there is no exit control.

Exit control is performed by the airlines when you check in on all flights entering and leaving the US. They send data to an inter-agency system called Advance Passenger Information System (APIS) run by CBP. There have been predecessors to APIS run by a variety of agencies since at least 2002.

APIS information at CBP.gov

APIS article on Wikipedia

Does an officer at a POE have access to all this information when you come back? That is perhaps a different question but the point remains the data is collected.

Walk across the border at Nogales and there's no exit control.

Never been a myth I've often said here, as have others, the information is collected.

There is an identical system in the UK to. It was up and running when I was working on border control, and it started about 7 years ago

Ditto San Diego/San Ysidro-TJ.

Yes they DEFINETLY do.
I was once pulled to a secondary interview at my point of entry and they questioned me as to my reasons on the number of days I had stayed in the US and the number of days out of the US (they read me the actual days, they had it on their files) over the last year or two.

What kind of Visa were you on?

Visa Waiver.
I'd never overstayed but had been "in" a bit too much.

So as long as you drive to Canada and take flights from there you'd be okay?

Those that think there are no exit controls are sadly mis-informed. About 4 yrs ago when I renewed my green card the INS (as it was) realised they had made a boo boo 10 yrs earlier. Anyway long story short in the process of correcting their error the were able to tell me every arrival and departure including time of day on some of them.

When you're a green card holder, when you "exit" what data do they have other than flight info in the airlines computer systems? I mean, if you're on a visa, the airline collects the stub of the form that you had in your passaport when you entered. But when you have a green card, you have no such stub. -Wait, or do you? In which case my memory has liquidated and I must have lost mine (the form stapled to passaport)

No form or stub, just your airline ticket (and passport).

OK. So the question stands. How would they know the exit dates of GC holders becuase the only data is that in the computers' of the airlines. And the previous poster mentioned he had been quoted his dates about 10 years ago by the INS - a time pre 9/11 and pre centralisation, I can't imagine they could have been collecting /merging and making sense of airline data.

Well you will have to cross into Canada, and if the officer at the port of entry inputs your information into their systems, then the US may have access to it, as the US and Canada do share information with one another.

I have no doubts that the government collate ALL passenger info into huge folders and have a list of everybody who has been in and out of the USA in the last 20 years or more.

Couple of times I have forgotten to hand in my I94 when I leave, and nothing has been said next time I enter, but that is only because my name has been automatically handed to the immigration system, as has the name and address, criminal record and marital status of every other person on my flight.

Every time I have checked in for international travel they take your passport number and every time you re enter US they scan your GC or run it through a little computer.

That is what made my situation so amazing. They could not figure out (given their error) how come I had never been pulled out for secondary checking.