Paul Krugman (who is, of course, a secret geographer) writes about small cities:
Some localized industries created fertile ground for new industries to replace them; others presumably became dead ends. And while a big, diversified city can afford a lot of dead ends, a smaller city can’t. Some small cities got lucky repeatedly, and grew big. Others didn’t; and when a city starts out fairly small and specialized, over a long period there will be a substantial chance that it will lose enough coin flips that it effectively loses any reason to exist.This is a fairly utilitarian take on city economies - that small places can't afford so many losing bets - but it does raise an important question about the optimum (or maybe sustainable minimum) size for a city. Now Krugman doesn't answer the question except to make the depressing observation that Christaller's central place theory no longer applies in a world where land, and more specifically agricultural production no longer determines the location or purpose of cities.
This idea of the service centre still persists. UK planning policies include the idea of a settlement hierarchy (pretty much straight out of central place theory) that ranks places according to their significance - small village, large village, local service centres, district service centres, towns, cities - with this ranking determining certain decisions about land use and related planning decisions. The idea behind this is that larger places meet needs that can't be met by smaller places. We all, sort of, recognise this idea because we will use it in our own choices - travelling to the big city for important gift purchases or big nights out because we expect the choice to be wider and more interesting.
This is the premise behind the 'megacity' - the agglomeration of all those services not only meets more needs successfully but also result in service innovation thereby meeting unanticipated or new needs. Such activity results in economic growth and betterment. Ergo the 'megacity' is a good thing.
Or is it? Here's a quote from Saskia Sassen who studies the megacity trend:
“These types of urban economies need other major urban economies more than they need the standardized production economies of other cities in their country,”As, Emily Badger, the author quoting Sassen notes, the implication is that San Francisco and London need each other more than they need the smaller cities in their domestic hierarchy of settlements. Indeed the international recruitment base (despite the obstacles of immigration controls) for high end skills and the dominance of 'megacities' in housing those skills means that the demographic profile of the megacity becomes less and less like the other cities in the hierarchy. On a personal emotional note, I certainly feel that, as a Londoner who left the city thirty years ago, it is a very different place - better in many ways but certainly different in style and feel. I suspect - on the boiling frogs principle - you have to leave and come back to see how places have changed.
So our question - when is a city big enough to sustain itself in a world of 'megacities' where the pull of such places on the best and brightest is huge. How big does a city have to be to have an economic gravitational force big enough to resisit all (or maybe just enough) of the force from the megacities?
Aaron Renn at New Geography gives us a start in a review of the US mid-west:
The clear dominance of the successful list by state capitals. This is so pronounced that I have put forth what I call the "Urbanophile Conjecture", which is that if you want to be a successful Midwestern city, it helps to be a state capital with a metro area population of over 500,000.The thing is that, by successful, Renn means 'not declining' and he focuses (good geographer that he is) on population rather than on economic measures like GVA. It's likely - given Krugman's gambling analogy - that 500,000 is nothing like big enough for a city to be sustainable, at least in economic terms. We have to get past the problem where one bad roll of the dice - a corporate bankruptcy, a crazy government decision or the decline of a given industry - cripples the city's economy and economic prospects. A city probably needs 1.5m to be sustainable (so Leeds and Bradford should, on this basis, become Britain's twin cities).
Tyler Cowan, in a commentary on Krugman's article, makes a couple of important points that help further. The first relates to the fact that people are not solely driven by economic considerations (a curse on Max U and all his works):
The very fact that smaller cities are used to consume non-pecuniary amenities suggests their inhabitants are more diversified than it may appear at first. The shift of gdp into services further enhances this diversification, and the new crop of semi-small cities may be more resilient than the older lot dependent on manufacturing.Those megacities are great - theatres, museums, restaurants, loads of young (and as some would say available) people, and economic opportunity galore - but what happens when what you want is a family, the wind in your hair, space to grow vegetables or fly kites? Cities struggle to offer these things and the bigger they are the less they do (unless you are very rich indeed).
Cowan's second significant point is another geographical point (one Krugman notes too) - while the cold, damp mid-western cities decline, America's sunbelt is booming:
A significant and enduring trend is the move into warmer and sunnier climates. So while Rochester and Flint decline, Chattanooga and Birmingham are on the rise.The original contention that smaller cities aren't sustainable because they don't generate sufficient chances for economics success begins to weaken despite those megacities sucking up the brightest and brainiest. Partly because they fail to offer services suited to a full human lifecycle - big cities (other than for the very richest) are not suited especially for children or the elderly and the process of settling down provides an opportunity for those mid-sized cities - if you're big enough to have some decent theatres, a few good restaurants and a range of cultural amenities plus near enough to green places and comfortable suburbs then you've a chance.
For me the answer lies in three things - dispersal, connectivity and development friendliness. The thing with megacities is that they are concentrated and want to concentrate further, they are intra-connected but only inter-connected to other megacities, and they are opposed to human-scale development preferring the grand, spectacular and tall. If you're a smaller city - say a sensible 1.5 million population with businesses in the modern economy - then urban containment, expensive mass transit systems and grand projets are the wrong strategy. You're not going to turn your town into London, Tokyo or New York and trying to do this could be a disaster (ask Barcelona).
There's no right answer to city size (indeed it's quite a deep wormhole in academic geography these days) but there is a case for being comfortable with being liveable and interesting rather than chasing the megacity rainbow. For smaller cities there needs to be more focus on suburbia, on family life and on amenities that allow for these things to thrive. Suburbia gets a bad press but the truth of the matter is that it's where most of us want to end up - house, garden, kids, good schools, safe streets, recreation grounds with youth football, family-friendly restaurants, a decent pub where you can sit down and chill. It you want your smaller city to work, these are the things you need and the life you need to sell - it's easier if you've decent weather and a beach but even without these things you can help develop a place people love and where folk want to come and live.