Macroeconomics 12th Edition by Michael Parkin

Exercise 6

Use the following news clip to work Problem.
Some Firms Struggle to Hire Despite High Unemployment
Matching people with available jobs is always difficult after a recession as the economy remakes itself, but the disconnect is particularly acute this time. Since the recovery began in mid-2009, the number of job openings has risen more than twice as fast as actual hires. If the job market were working normally, openings would be getting filled as they appear. Some 5 million more would be employed and the unemployment rate would be 6.8%, instead of 9.5%.
Source: The Wall Street Journal , August 9, 2010
If the labor market is working properly, why would there be any unemployment at all