How in the name of all that is holy does the government ascertain how many people WANT a JOB?
By definition, if someone entered the workforce, the assumption is they want a job. Duh!
Its not difficult to figure out how many people are entering the job market for the first time in any given month. Its called demographics. For example, all the people that are going to support the baby boomers in their retirement are already born and most of them are already working. From past history, the demographers know how many people are going to enter the workforce each month of the year. If you know population growth and keep a tab on trends like more working women and more people with two jobs, its fairly easy to estimate the number of people entering the job market.