Over the river and through the wood is more complicated in these days of air travel. At least those scheduled to leave soon for holiday trips can take comfort knowing that flying to and from Chicago is generally less expensive than similar roundtrips from other U.S. cities.

How much less? Well, that’s a pickle. The science of airline pricing is notoriously capricious. Everything from fuel surcharges to reasons for traveling (business or pleasure?) factors into ticket cost, and literally tens of thousands of prices change every day.

A handful of easily measured factors carry the most weight, however: distance between airports, time of year (yes, Virginia, prices do go up for Christmas), and competition among the carriers serving the route. “The airlines hate each other with a passion,” says Rick Seaney, CEO of Farecompare.com, “and will do anything they can to try to finagle market share from each other.”

The Dallas-based Seaney points out that Chicagoans are lucky that big players like American and United duke it out at O’Hare—and that they also fight Southwest over at Midway. “Flying out of Chicago is much cheaper than out of Dallas, in spite of the fact that [O’Hare] and DFW [Dallas–Fort Worth] are in the top ten busiest airports worldwide,” Seaney says.

Or, as Joyce Moynihan, AAA-Chicago’s regional travel manager, puts it, “Chicago is a great place to live in terms of visiting other folks.”

By the Numbers

Using the meta-search tool at Kayak.com, we averaged roundtrip ticket prices between Chicago; Dallas; Washington, D.C.; San Francisco; Los Angeles; and New York for all available airlines and airports for an early morning flight departing on Wednesday, November 21st, and returning Saturday, November 24th. (Flights generally increase in price later in the day.) We used the cheapest ten tickets as our yardstick, unless there was a big gap in price between tickets that no sane person would ever cross. And to account for the airline’s overhead costs, we started our analysis by knocking $150 off the price of each roundtrip, then calculating the per-mile rate for the rest of the cost. To find the cost for each pair of cities, locate them on the left side and bottom of the chart, then follow up and to the right to find the box where they intersect. (It’s worth noting that these prices come from early September. Airfares rise and fall–—mostly rise–—the closer you get to your departure.)