In July 2019, there were 1.5 million people who were marginally attached to the labor force, essentially unchanged from a year earlier. These are people who were not in the labor force, although they wanted work and were available for it and had looked for jobs at some point in the previous 12 months. They were not counted as unemployed because they had not actively searched for work in the 4 weeks preceding the survey.

These people are referred to as the  discouraged workers.A person who is eligible for employment and can work but is unemployed currently and has not attempted to find employment in the last four weeks

Explanation:

Discouraged workers are the individuals who is eligible for employment and can work but is unemployed currently and had not made any attempt to find employment in the last four weeks.

For example: Young graduates,senior citizens.

Discouraged workers are not considered as a part of the labour force and are  not counted in most official unemployment rates.

These are people who were not in the labor force, although they wanted work and were available for it and had looked for jobs at some point in the previous 12 months. They were not counted as unemployed because they had not actively searched for work in the 4 weeks preceding the survey.

If unemployed workers become discouraged, the measured unemployment rate will fall