The unemployment data for September released last month showed that for the eighth month in a row, the unemployment rate in the Pittsburgh Region had decreased from a year ago.

In fact, the Pittsburgh Region has had one of the largest decreases in the unemployment rate this year among the top 40 regions in the country. The average unemployment rate here between January and September of 2007 was 4.4 percent, compared with 5.1 percent during the same nine months in 2006.

That's really good news, right? Unfortunately, "no" -- as it turns out, it's exactly the opposite. The unemployment rate in the Pittsburgh Region has been decreasing not because people are getting jobs, but because people are leaving the work force, and many of them may be leaving the region altogether.

Many people believe that the unemployment rate is the percentage of the population that doesn't have a job. But it's actually the ratio of the number of people who are looking for work divided by the "labor force," and the labor force is defined as the number of people who are either working or who are looking for work.

Every month, the labor force changes size because people either start looking for work or stop looking for work.

This means there are two different reasons the unemployment rate can go down. One is that people who are looking for work find jobs. But the unemployment rate also will go down if people who can't find jobs give up and/or move away, i.e., if they leave the labor force entirely.

What's happening in Pittsburgh? The Pittsburgh Region is one of only three regions in the country where unemployment has decreased primarily because people left the labor force, rather than because of an increase in employment. Comparing the first nine months of 2007 and 2006, the number of unemployed people in the Pittsburgh Region decreased by 8,100, but the number employed increased by only 2,200.

The primary reason for the decline in unemployment was that the number of people in the Pittsburgh labor force decreased by 5,900 (a 0.5 percent decrease).

In contrast, Dallas saw its unemployment rate drop by an amount similar to Pittsburgh's -- from 5 percent in the first nine months of 2006 to 4.3 percent in the same period in 2007. But there, the labor force increased by nearly 36,000 (a 1.2 percent increase), and employment in Dallas increased by more than 56,000, enough to reduce unemployment by more than 20,000 and still absorb the 36,000 new workers who joined the labor force.

In fact, the Pittsburgh Region has had the largest percentage reduction in labor force this year of any of the top 40 regions in the country. That's why we've had such a large decrease in the unemployment rate. It's hard to know the reasons, but anecdotal evidence suggests that many are giving up and going elsewhere.

It's not surprising if they're discouraged -- there were only 3,000 more jobs in the Pittsburgh Region in September than a year ago, a growth rate of only a quarter-percent, and we still have 5,000 fewer jobs than we did in 2001. Job growth in Pittsburgh was less than one-fourth the national rate and was slower than all of the top 40 regions except for Cincinnati, Cleveland, Detroit and Providence, R.I. And it's getting worse, not better.What's causing our slow growth? It's not US Airways cutbacks or a few major plant closings. The economic malaise cuts across almost every sector of our economy. The most likely causes are an uncompetitive state business climate and insufficient support for entrepreneurship.

And unless we fix those things, we can expect to lose more of our labor force in the months ahead.