In February 2008, the household survey indicated that about 250,000 people lost or left their jobs. At the same time, though, the ranks of the unemployed declined by nearly 200,000. The counterintuitive result was that the number of unemployed workers fell even as the economy was shedding jobs. What explains both a drop in employment and a reduction in the number of workers considered unemployed by the BLS

The result can be explained by the fact that about 450,000 people got new jobs.  This means that the 250,000 that left their jobs actually got new jobs in addition to 200,000 others who also got jobs (perhaps as replacements for the 250,000 that relocated jobs) after being unemployed for some time.

Another possible explanation may be as a result of some drop in the population resulting from aging and death, which causes a decline in labor force participation.

Explanation:

A drop in unemployment rates foreshadows that the economy is rebounding.  This is a good sign of economic recovery.  When new jobs are created due to technological advancements, people tend to move from one job to another, and those open positions are quickly refilled from the pool of the unemployed.  This means that productivity will be on the increase, and the economy will be the better for it.