"It’s really mostly related to density. And what we find is that if you are in a rural area where you don’t have many people per square mile, the cost of public services is rather high," says Walden, a professor of agricultural and resource economics at N.C. State University.

"Then if you move to an area where the density has increased a little bit, those governments there are able to employ more economies of scale, and the cost of public services will go down.

"But then as you move up the ladder of density and you get into some really high dense areas -- in North Carolina, that might be in some areas like in Raleigh and Charlotte; certainly nationally in areas like New York City, Philadelphia, et cetera -- then we see the costs go back up.

"So you kind of have this U-shape where you get very high costs of public services in low-dense and very high-dense areas, and you get the lowest cost of public services kind of in the middle-size cities.

"And this is an issue that government people have to face all across the country," Walden concludes. "It does cause some issues, especially in fast-growing areas."