What a mid-sized city is? As the readers of this blog are scattered through diverse areas, the best way to define this concept would be a qualitative rather than a quantitative one. There is a Federation of Mid-sized Cities in France that groups those that are central and have 20.000-100.000 residents, but this is difficult to extrapolate. Porfirio Diaz, who presided Mexico in the later XIXth century, is said to have lamented “poor Mexico, so far from god and so close to the United States”. A mid-sized city is probably as far or as close to god as its dwellers allow, but in geographical terms it is far enough from a megalopolis to have a certain independent life and to polarise the dynamics around it.
The mid-size city: a qualitative condition
The demographic or economic weight of a city is not nearly as important as its ability to create those links and to develop them over time. In that sense, a mid-sized city could well be called a mid-rank city, as it occupies an intermediate situation in an urban network, and it could not even be the most populated city in a metro area. Besides, the distance at which a city can be considered to have some independence from a megalopolis does not respond to a fixed rule. Independence is also a fuzzy concept in an interlinked world.
You can sometimes hear that mid-sized cities have a better quality of life than mega-cities. That can be true, but they can also be less resilient in a crisis if their economies are not diverse, and remember that theorists usually agree on the fact that economic diversity requires a certain size. So perhaps the best way to get a better view is to look at several mid-sized cities (chosen with my imperfect knowledge) to try to get some conclusions.