Who just stops looking for a job? Those who can live off the income of another I would suppose; spouses, adult children. I think a poll asking such a question would have a high margin of error as a person's pride comes into play. People may say they've stopped looking, even tell themselves they've stopped looking, but they still look, just not as much. It is said looking for a job is a full time job. After maybe 18 months of dejection, they go into part time job hunting mode and since they cannot say they've found employment, "I've stopped looking." maintains one's sense of dignity.