One way to measure the vibrancy of a business community is by its new-company formation.

Think about a Silicon Valley which is celebrated for producing technology companies in all flavors.

When you look at the Philadelphia region, there would seem to be a lot of promising ingredients to spawn and nurture new enterprises:

* Good location between the financial capital (New York) and the actual Capitol (Washington, D.C.);

* Concentration of more than 60 colleges and universities;

* Home to large corporations that depend on new ideas from small firms, such Big Pharma and information technology for the financial sector;

* And even a small seed- and early-stage funding network that can provide the first capital to the next generation.

But then, I read a report called “Kauffman Index of Entrepreneurial Activity, 1996-2007.”

This index measures the rate of business creation at the individual owner level. Sponsored by the Ewing Marion Kauffman Foundation, the index draws on Bureau of Labor Statistics and Census data to come with an overall business creation rate.

For the United States as a whole, 300 out of 100,000 adults created a new business each month during 2007. That rate has been pretty consistent since 1996, dipping as low as 270 and as high as 320.

Pennsylvania and Philadelphia have a certain consistency too: We’re lagging the United States.

In Pennsylvania, 150 out of 100,000 adults created a new business. (We outpaced only West Virginia with 80, Alabama with 100 and Delaware with 140. New Jersey had 260.)

The states with the highest activity? Idaho, the District of Columbia and Arizona were tops with 460 per 100,000 adults.

The numbers were crunched by Robert Fairlie, an economics professor at the University of California at Santa Cruz. He also looked at the nation’s 15 largest metropolitan areas. Philadelphia is the fifth-largest metro area, but it was dead last for entrepreneurial activity at 110 business owners per 100,000 adults. In contrast, Phoenix blazed along with 580 entrepreneurs per 100,000 people.

It was too much hope that maybe it was a one-year thing. Fairlie said the three-year average for Philadelphia was 170. Considering that 2006 was a strong one for the economy, it’s troubling that Philadelphia could muster only 230.

Fairlie says that construction is a big contributor to total business creation. And that may be what this report is really showing. For all of cranes around town, Philadelphia never boomed in the real estate bubble. We also didn’t create tons of construction-related businesses that might be going out of business now in the housing slump.

Without a doubt, one of the hardest hit areas in the nation is the Detroit metro area. The auto industry has really struggled and the region has one of the highest foreclosure rates. Still, Detroit matched the national entrepreneurial activity index at 300.

So Detroit hits 300, while Philadelphia is mired in a slump at 110. Where have all the entrepreneurs gone?