EXAMPLE 10 Measuring unemployment again

Measuring unemployment is also “measurement.” The concepts of bias and reliability apply here just as they do to measuring length or time.

The Bureau of Labor Statistics checks the reliability of its measurements of unemployment by having supervisors reinterview about 5% of the sample. This is repeated measurement on the same individual, just as a student in a chemistry lab measures a weight several times.

The BLS attacks bias by improving its instrument. That’s what happened in 1994, when the Current Population Survey was given its biggest overhaul in more than 50 years. The old system for measuring unemployment, for example, underestimated unemployment among women because the detailed procedures had not kept up with changing patterns of women’s work. The new measurement system corrected that bias—and raised the reported rate of unemployment.