"If we assume that everyone in US cities with >500,000 people makes two elevator round-trips per day, the US is losing out on 270 days of worker days per day or

"If we assume that everyone in US cities with >500,000 people makes two elevator round-trips per day, the US is losing out on 270 days of worker days per day or $13 million per year. Each elevator used wastes $160 per year. If your elevator was installed x years ago and your contractor charges you y per hour and takes z hours to invert the buttons, should you inver them? Return ((25-x)160-yz >= 0);" Sorry but this is absolute garbage. I hate when people take a meaninglessly insignificant value, and then extrapolate it out to come up with a ridiculous dollar value, to try to prove a point. 270 worker days because of elevator buttons? Imagine how much the US loses because people sit on the toilet for 2 mins longer every day because they play Words with Friends. I assure you that lost productivity completely outweighs any time spent figuring out which buttons to press on an elevator. Another error on your part is that you even said yourself that familiarity with the button layout will improve the time. So basically, if the same person is using the same elevator over and over again, it can't improve much further after a few attempts. It's only the first 10 times that the person actually might take more time, and after that it has reached the optimal level. Sorry to be blunt, but you should abandon this project. It's not useful at all.