The U-6 unemployment rate, also known as the “real unemployment rate,” is a more comprehensive measure of unemployment than the regularly reported U-3 rate. While the U-3 measure of unemployment considers only people who are actively seeking work and have been unemployed for less than four weeks, the U-6 takes into account a wider range of labor market participants.

In addition to the U-3 definition, the U-6 also includes people who have given up looking for work, those who are employed part-time but who would prefer to work full-time, and people who are "marginally attached" to the labor force. These individuals have likely taken themselves out of the job search agent, either because they have been unable to find a job or because of other reasons such as the availability of benefits, childcare costs or transportation issues.

The U-6 rate provides a more accurate account of labor market conditions than the U-3 rate, as it provides an enlarged view of unemployed and underemployed workers in the economy. While the U-3 rate does not provide useful information about the underlying level of economic slack, the U-6 rate does, as it includes a broad range of labor market participants who would benefit from an expanding economy. As such, it can be used to gauge the health of the broader labor market in a more comprehensive way than other measures.

However, while the U-6 rate offers a more complete picture of the labor market, it can also be misleading at times. The rate can be impacted by seasonal fluctuations, as well as changes in labor force participation rates, and so it may not always display a true picture of the economy.

In short, the U-6 rate is an important tool in assessing the labor market situation. It provides an expanded view of labor market conditions, which can allow economists to better understand the level of economic slack in the economy. While it is not without its limitations, it is an important indicator that can be used to gauge the health of the labor market overall.