David Leonhardt, a journalist for the New York Times, wrote in March 2008 that “the average unemployment rate in this decade, just above 5 percent, has been lower than in any decade since the 1960s. Yet the percentage of prime-age men (those 25 to 54 years old) who are not working has been higher than in any decade since World War II.” In other words, even though the unemployment rate was low, the employment rate is declining. Given how the BLS measures the unemployment rate, explain how this seemingly inconsistent observation could happen.