In a study of businesses on walkable main streets in three Massachusetts towns, business that were used as "third places" (a place of refuge where people can regularly visit and commune with friends, neighbors, coworkers, and even strangers) had significantly more outdoor seating and shade devices than other comparable businesses. "Third places" also tended to have higher amounts of personalization and permeability to the street.
Mehta, Vikas, and Jennifer K. Bosson. (2009). Third Places and the Social Life of the Street. Environment and Behavior 42(6), 779-805.