pot equity

[mmctrab]

Okay, please help a newbie out. How does pot equity change preflop according to the number of people in the hand? For example, in a limit hold'em game, if 4 people limp in front of me, and I hold pocket Jacks, I understand that my pot equity is greater than 20% so I should raise.

But, what if only 2 people limp in front of me? Does my pot equity increase proportionally with the reduction in limpers, or is there a point where raising the Jacks becomes incorrect from an expectation standpoint? Thanks.