Can HN managers throw some light on this ?
Layoff 1: The manager knew in advance, and couldn't tell us. But rumors were flying. In a team meeting on Friday, someone asked about the layoff rumors. She specifically said, "I can't say". Someone alertly asked "Can't say, or don't know?" She replied, "I can't say." So we all knew. Most of us got laid off on Monday morning.
Layoff 2: I was feeling uneasy. I walked into my boss's office, closed the door, and asked, "If you were in my shoes, would you have your resume on the street?" He said, "No, I think you'll be fine." The next day he got laid off. I didn't. He pretty much knew it was going to go down that way.
Layoff 3: My boss knew it was coming, because he walked past a meeting room that contained what he described as "an odd collection of managers" - and not him. From that, he surmised that there was a layoff coming, that they were figuring out who to lay off, and that, since he wasn't in the room, it was going to get him. He still didn't tell us beforehand.
So in all three cases, the managers knew or could make a pretty good guess.
And, one bonus story that didn't happen to me: I have heard of a legendary layoff at Evans & Sutherland. They laid of some managers, and some team members, but not every team member of the laid-off managers. And they botched it by first laying off the managers. Then, when it came to the workers, some of them didn't have managers to do the layoff. So IT logged everyone off of the network. If you could log back in, you still had a job. If they had killed your account, you were laid off.
If you're losing 80% of employees, that's more than a layoff. That's a severe restructuring of the entire business.
Your managers very well might not have been informed until the last minute. These things are best handled all at once, rather than slowly leaking information out to different levels of employees over time.