I am no macroeconomist; however, I think there are some important dots to connect between cities and economic growth. The Gated City by Ryan Avent, (discussed more in depth here), explores this thesis and offers a nice overview of the research that links population density and productivity. He cites Ed Glaeser and others who see a strong correlation between the two. Glaeser finds that with a 50 percent increase in population density, productivity increases by 4 percent.
Additionally, I find Geoffrey West’s work (not cited by Avent) particularly intriguing. West is a former physicist who has studied the correlation between city size and all sorts of variables from the number of gas stations to the number of bank deposits per year. He’s found that every time a city doubles in size, worker productivity increases by 15 percent. The distinction between West and many others who study this issue is that he focuses on a city’s total population rather than its population density.
Increasing worker productivity is the holy grail of macroeconomics. As worker productivity grows, it raises our wages and standard of living. This is what lifts poor countries out of poverty and ensures that future generations will enjoy a higher standard of living than we do today. Some of the factors that economists widely agree contribute to higher growth rates include education, property rights, and rule of law. Perhaps urbanization should be added to the list too.
I won’t weigh in here on whether the variable that influences productivity is population size or population denisty; maybe they both do. In the context of land use policy, I would argue that it doesn’t matter which variable we look at. By limiting development, land use restrictions typically lead cities to be both less dense and of smaller populations. This applies equally to traditional land use restrictions and to Smart Growth policies like urban growth boundaries.
I would never suggest that lawmakers should undertake efforts to incentivize, or even “nudge,” people to move to cities. However, given all of the data that suggests that people are more productive in cities, policies that limit urban growth should be treated with extreme caution. In the ongoing discussion of how to get people to pay attention to the costs of land use regulation, this argument should carry some weight as economic growth remains lackluster in many parts of the world.