According to the On Numbers Economic Index, Seattle ranks 40th in the nation, well behind top performers Oklahoma City, Autin and Omaha. The index is a product of American City Business Journals, which publishes regional business journals across the country, including the Puget Sound Buxiness Journal.

The American economy is strongest in the heartland.

Oklahoma City, Austin and Omaha are the highest-rated markets in September’s version of the On Numbers Economic Index, which measures the economic health of 102 major metropolitan areas.

The top eight metros, in fact, are far from the Atlantic and Pacific coasts. All eight lie within a triangle that has Houston, Pittsburgh and Denver as its endpoints.

No. 9 Boston is the strongest market on either coast. Only four other coastal metros — Charleston, S.C. (13th), Portland, Maine (16th), San Jose (17th) and Honolulu (20th) — are in the national top 20.

The index doesn’t examine public policies and the business climate. Rather, it looks solely at performance measures using

an 18-part formula that assesses private-sector job growth, unemployment, earnings, housing-price appreciation, and construction and retail activity. Here is the detailed methodology.

Still, looking at the abundance of high-performing heartland cities – typically places with lower business costs, affordable housing and good public services – some business climate implications may be discerned.