Legs, more or less

Economy, plus 10%? United Airlines, in retrospect, may have done something very smart. Back in the late 1990s, United said it would separate as much as one-third of its regular coach seats by as much as five inches more, dub it Economy Plus and set an additional fee on a sliding scale over regular coach fares. The carrier has never promoted Economy Plus heavily, but it it may be on to something.
Evidence of that comes from seatguru.com, the on-line service that just completed a survey that found its members would pay as much as 10% more for a little extra legroom. Some 42% of seatguru.com readers would pay for about five inches of added legroom. The same seatguru.com readers said that JetBlue has the best economy seats. That leads to the question, do they know that a chunk of JetBlue seats (in rows 11 through 25 in the all-coach cabin) just happens to have as much as five extra inches? And the carrier charges extra for only some of these seats?
(Illustration from United's website section on Economy Plus.)