Same as how you ask for it in GREAT economic times -Lay out your contributions... the profit you bring to the company.. show off.
If you got all that, tough economic times only mean they can't afford losing you. It's actually a leverage.
Needless to say, however, the demand must be a reasonable one.
Because economy is not something flexible. If you ask something they can't give, they can't keep you even if they want to.