By DANIEL HAMERMESH

I earned two free one-way coupons on Southwest Airlines. I tried to redeem them for a round-trip flight in March, but there were no coupon seats on the return flight. So I redeemed one coupon, and have one left over. That’s a clever strategy by Southwest, as I will now use the other coupon as part of a second round trip.

to read more, visit: http://freakonomics.blogs.nytimes.com/2010/02/04/a-good-reason-to-fly-so...