This paper evaluates the simplifying assumption that producers compete in a large market without substantial strategic interactions using nonparametric regressions of producers' choices on market size. With such atomistic competition, increasing the number of consumers leaves the distributions of producers' prices and other choices unchanged. In many models featuring non-trivial strategic considerations, producers' prices fall as their numbers increase. I examine observations of restaurants' sales, seating capacities, exit decisions, and prices from 222 U.S. cities. Given factor prices and demographic variables, increasing a city's size increases restaurants' average sales and decreases their exit rate and prices. These results suggest that strategic considerations lie at the heart of restaurant pricing and turnover.