Perhaps urban planners do not have long enough time horizons

Hmmm.  

Urban planners everywhere are indulging in their authoritarian obsessions with how people ought to live in cities.  Ought according to the planners.  Plans and fads with which people often disagree and simply respond to by leaving.  Hence, doughnut cities - thriving suburban and exurban metropolises around dysfunctional holes where a downtown used to exist.  

One of the fads, or rather a combination of them, are livable cities, walkable cities.  Some interesting ideas in there but usually conveyed in an autocratic way, without consent of the governed and almost always implemented badly and with failure as the outcome.  

But that's  the history since World War II across much the western world - Detroit, St. Louis, Atlanta, Newark, Kansas City, etc. in the US but Coventry, Manchester, Belfast, etc. elsewhere in Europe.  Regionally prosperous but a struggling and generally dysfunctional historical core jurisdiction.  

Those seventy years are an aberration.  While there were ebbs and flows, most cities in the OECD before WWII always exhibited a sustained long term growth with occasional sharp demographic plunges owing to the Four Horsemen of the Apocalypse.  

Reading an old post from 2016, Cycles of famine, war, and plague as pressures of evolutionary change, made me think of this post-WWII history in a different light.  

So I remain skeptical, but here are some of the passages from The Pursuit of Glory: The Five Revolutions that Made Modern Europe 1648-1815 which cause me hesitation and reflection. Pages 43, 53 and 59

Following the catastrophic population losses caused by the Black Death in the middle of the fourteenth century, recovery began in the late fifteenth and continued throughout the sixteenth. But around 1600, the Four Horsemen of the Apocalypse returned with a vengeance to many parts of Europe, bringing war, plague and famine with devastating demographic consequences.The great plague which struck Castile in 1599-1600, for example, was only the first of many such visitations which reduced the population of the region by a quarter by 1650.

[snip]

It has been estimated that during the terrible mortalite of 1692-94, 2,800,000 people, or 15 per cent of the total population of France, perished. The 1690s proved to be particularly destructive all over western, northern, central and eastern Europe. In Finland the famine of 1696-7 carried off at least a quarter and perhaps as much as a third of the population. In Scotland, a poor harvest in 1695 was followed by severe failure in 1696, a modest improvement in 1697 but general failure in 1698. In the worst affected counties, such as Aberdeenshire, the mortality rate reached 20 per cent. As Sir Robert Sibbald observed: "Everyone may see Death in the Face of the Poor.'

[snip]

Some idea of the havoc inflicted by plague can be gained from simple statistics: Naples lost about half its population and Genoa 60 per cent in 1656; Marseilles and Aix-en-Provence lost half in 1721; Reggio di Calabria lost half in and Messina 70 per cent in 1743; Moscow lost 50,000 or about 20 per cent in 1771-2, and so on.

I have also since 2016 also read Daniel Defoe's Journal of the Plague Year when London lost about 25% of its population over the course of two years.  

All these cities were very dense for their times and technologies, with density always increasing owing to changing technology.  

Look at the five cities in the US with the greatest shrinkage.  

St. Louis - shrank 65% from 860k to 300k

Detroit - shrank 64% from 1.9m to 385k

Cleveland - 58% from 920k to 670k

Buffalo - 59% from 580k to 300k

Pittsburg - shrank 65% from 675k to 300k

Sure, 1960s race riots, 1970-80s rustbelt, rise of the service economy, etc.  Lots of explanations for why they shrank, but those are huge rates of shrinkage over quite short periods of time.  Outmigration basically took much of the sting out of the process but still . . . a massive loss of potential.

Other notable American shrinking cities include Chicago, Baltimore, Milwaukee, Hartford, Rochester, Memphis, San Francisco, and Birmingham.  

Expansive suburbs and exurbs grow, dense downtowns shrink.  With lots of commentary and to some degree real personal disruption but by and large not societal disruption.  Not losing 25 of your population to death in two years kind of disruption.  

Worldwide in the OECD countries, almost all of them have now entered demographic decline.  Not just populations moving out of cities but the population size shrinking in absolute terms.  This has been most prevalent in some dense countries such as South Korea and Japan but has been spreading everywhere.  

Shrinkage of city centers is so second nature to us that perhaps we might be not seeing something that we should notice is there.  We observe city centers shrinking and losing economic dynamism (while suburbs and exurbs grow).  Separately we have our Urban Planners obsessively focusing on making city centers more dense and less auto-friendly.   This is largely driven by ideological/utopianism.

But I rarely see any discussion integrating the two discussions.  Where will the densification discussions go (with all their associated cost and and functional trade-offs) when, on average, in many if not most places, cities are shrinking?  

And more to the point of this post, what if densification is inherently detrimental to public health?  

Pre-World War II, for centuries, we have been accustomed to dense cities getting denser but also getting sicker and more frequently having larger die-offs of 10%, 15%, 20%, 25%, 30% die-offs in a year or two every few decades.  

The last seventy years since World War II has seen astonishing rises in global trade, rises in global prosperity, and rises in health technology and health infrastructure.  

But what if we step back and look at it all from the perspective of centuries?  What if these seventy years have been a fortunate anomaly?  An anomaly where prosperity, technology and health infrastructure in combination with out-migration from dense city cores have helped us in an unintended fashion to avoid the early pattern of periodic mass die-offs?  

Have we permanently escaped that cycle or is it a mere interregnum?  

What if the urban planning fad for car free, walkable, dense cities actually is hastening a return to the previously observed pattern of periodic mass die-offs?