Recently, I boarded a flight from Seattle to Houston. I was in seat 10C, an aisle seat. The middle seat next to me, 10B was empty. Across the aisle, 10E, the middle seat was also empty.
A mother and father, holding a young infant, were complaining to the flight attendant that they wanted to sit together, but there were no other seats next to each other. I volunteered to move from my aisle seat (10C–which I paid more for, United EconomyPlus) to the middle seat, 10B. Now, I was sandwiched next to a mom holding a crying baby. Lovely.
A few moments later, the mom passed the baby over to the dad, who was now sitting in the other middle seat, 10E. This was going to be the routine. Pass the crying baby across the aisle.
The guy who was sitting in 10F, the other aisle seat, made a smart decision. He offered to switch seats with the mom sitting next to me. Now, the mom and dad were sitting next to each other with baby in 10E and 10F. I’m still in the middle, but minus the crying baby.
These exchanges were Pareto Optimal. Had I remained in my aisle seat, and not volunteered a change, I would’ve had a crying baby next to me. Likewise, if the guy in 10F stayed in his seat, he also would’ve had to sit near a crying baby. Plus, the disruption of passing the crying baby back and forth. Now, both of us, who volunteered to take different seats, are slightly better off than if we had stayed put. The only person who is worse off is 10D, who remains next to the crying baby in the window seat.