Greater Hartford has a higher concentration of jobs at foreign-owned firms than two-thirds of the nation's biggest urban areas, according to a study from Brookings Institution released Friday.

Fairfield County has the highest proportion of jobs at foreign firms in the country — more than 13 percent.

That matters because foreign direct investment tends to be concentrated in high-value fields — and as a result, foreign companies with operations in the United States are above average in research and development spending, productivity growth and employee compensation.

The study's authors, however, note that recruiting foreign firms isn't a tool for job creation — and most of the additional jobs at foreign companies over the 20 years came through foreigners buying existing companies, not opening new offices or factories.

For instance, Ahlstrom, a Finnish paper company, bought Windsor Locks' Dexter Corp in 2000.

In Greater Hartford, Stop and Shop is the single biggest foreign employer — the grocery chain is owned by a parent company in the Netherlands.

Architecture and engineering is second — Cyient, an Indian-owned firm, is an example of an engineering firm with nearly 500 jobs in central Connecticut.

The third-largest concentration is in insurance — Hartford Steam Boiler is now owned by Germany's Munich Re.

Metalworking machinery is the specialty at Trumpf, a German firm with about 500 workers in Farmington — fourth on the list.

And rounding out the top five was fabrics, including Ahlstrom's specialty coated fabrics and Warren Corp. in Stafford Springs, owned until last year by an Italian firm. That company just returned to U.S. ownership Wednesday.

The study is a snapshot of foreign investment in 1991 and 2011.

The most effective economic development approach to foreign firms, the authors say, "does not treat foreign direct investment attraction as an end in itself but rather regards it as a tool for strengthening industry clusters, infusing new knowledge and technology into U.S. production systems, and increasing global engagement in U.S. regions."