Most companies started laying off around 2007/2008 when the economy started sinking from the housing burst. I believe alot of them just took advantage of the situation to lay off during this time so they wouldn't look so bad, use the bad economy as an excuse.
Also alot of buy-outs & mergers are a cause for layoffs.
Now companies that are hiring are hiring people at lower wages and working them longer hours.
"One Nation Under A Groove"