Final answer:
The U.S. Bureau of Labor Statistics calculates the national unemployment rate as the ratio of those counted as unemployed to the civilian labor force.
Step-by-step explanation:
The national unemployment rate in the United States is calculated by the U.S. Bureau of Labor Statistics (BLS) using the ratio of those counted as unemployed to the civilian labor force. This means that the unemployment rate represents the percentage of individuals who are actively seeking employment but do not currently have a job, relative to those who are part of the labor force. It is important to note that the unemployment rate is not based on the entire civilian population, but specifically on those who are part of the labor force.