http://consumerist.com/2007/09/12/researchers-find-that-shopping/

Researchers find that shopping malls can encourage healthier “incidental activity” by placing signs next to stairwells that read, “Take the Stairs,” which caused a 190% increase in stair activity over three weeks. Or, just do what most the stores in NYC do and make sure at least one escalator is out of service at all times. [Reuters]