When you think about where the fastest-growing private companies are–and the jobs they’re creating–the Philadelphia region is probably not top of mind.

That may be changing. According to an analysis of Inc. Magazine’s latest Inc. 5000 list of fastest-growing private companies on its website yesterday,  the Philly metro area ranked No. 7 with 151 companies on the list, which was more than Boston, San Francisco, Seattle, Austin or Denver, all of whom are considered more well-known startup hubs.

And, according to Inc., this isn’t a one-year phenomenon. The magazine said that since the end of 2012, the fastest-growing private companies in the Philly metro area have added a whopping 57,000 new jobs, ranking it the No. 2 in overall job growth.

It’s unclear what has accounted for this hiring binge, but Inc. suggests that a lower cost of living and cheaper wages (in addition to good location and abundant amenities) are factors likely driving the hiring binge.

There are, however,  several caveats with regard to the jobs data, which is self-reported by the companies. As Inc. noted, the head counts include human resources companies, which may be overrepresented as employees on the payroll might not include actual company employees. Put another way, these companies tend to skew the numbers.

Inc. said the head counts are self-reported by each company as of the last day of 2015 and Inc. compares the data with that of year-end 2012. The definition of employee also includes seasonal workers receiving any level of benefits, such as basic paid national holidays.