NOT IN THE LABOR FORCE:
Anyone who is not classified by the Bureau of Labor Statistics (BLS) as members of the labor force, either employed persons or unemployed persons. This catch-all category is largely comprised of several notable segments of the population, such as young, elderly, homemakers, and military. However, it includes others who are either unwilling or unable to engage in productive activities for assorted reasons. The "not in the labor force" numbers are computed monthly by the BLS along with other employment and labor force information using data generated by the Current Population Survey.
The combination of employed persons and unemployed persons is the official specification of the civilian labor force, meaning anyone who does not qualify for the civilian labor force is classified as "not in the labor force." Some people are excluded automatically by virtue of their demographic characteristics, and others are excluded by virtue of decisions they make.
Automatic Exclusions
Three of the seven basic groups not in the labor force are automatically placed in the not in labor force category due to the basic specification of the "noninstitutionalized civilian labor force." They are the young, military personnel, and institutionalized members of the population.
Young: Anyone under 16 years of age is automatically placed in the not in labor force category by the BLS. The reasoning is that these young folks do not work, so why bother. More specifically, child labor laws legally restrict the employment of anyone under 16 years old from working, except in special cases (child actors and farm labor are two). In addition, laws also require anyone under 16 years old to attend school, so they are not generally available for work. Social customs also limit the employment of anyone under 16 years of age.
Military: Military personnel are also automatically relegated to not in labor force status. This segment of the population is excluded from the civilian labor force because military personnel are not considered as resources available for productive activity. Moreover, the military operates under its own set of "employment" rules, apart from resource and labor markets that exist in the rest of the economy. The reasoning behind excluding this segment is perhaps most obvious during periods of rising and declining military activity (that is, during and immediately after wars). If military personnel are included in the labor force, then a major movement of civilians into the military has no apparent affect on the labor resources available for productive activity, when in fact, the quantity of labor available for domestic production declines.
Institutionalized: Members of the population who have been institutionalized are also automatically excluded from the "noninstitutionalized" civilian labor force. The institutionalized population includes people in correctional facilities (prisons and jails), mental or psychiatric hospitals, and nursing homes. This segment of society, much like those under 16 years of age, is excluded because these folks are essentially unavailable for productive activity.
Excluded by Choice
Four other basic groups that make up the not in the labor force category are there largely by choice. In many cases, individuals in these groups have consciously decided to pursue other activities and to exclude themselves from employment possibilities. In other cases, they have pursued a particular path that largely prevents them from entering the labor force. The four groups are homemakers, students, elderly, and marginal workers.
Those are homemakers, students, elderly…no surprise there. this is the category that allows over 100m to just be a statistic:
Marginal Workers: A last group of individuals who have decided to be apart from the labor force is workers who are marginally-attached to the labor force. The broad group includes those who are willing and able to work, but have been unemployed and have stopped seeking employment. Marginal workers largely include discouraged workers who have stopped seeking employment because they believe no jobs are available, as well as others who stopped looking for other reasons.
http://www.amosweb.com/cgi-bin/awb_nav.pl?s=wpd&c=dsp&k=not+in+the+labor+force>>4886469