They would be counted as not in the labour force because they are unwilling to take a job if it were offered.

They are not included in the participation rate as they cannot easily find work.

They could have previously worked in an industry that was declining in size because jobs in this industry are being shifted off shore.

They are unemployed for only short periods of time as they can easily transition from job to job.

They are not in the labour force because they have stopped actively searching for work.