Two examples come to mind:
in practice, similar proposals (that have actually been implemented, both in communist and nominally capitalist countries) have vastly underestimated the difficulty of this problem, leading to large problems that have made life harder for many people
Singapore and Hong Kong are two generally-capitalist cities that have employed largely government housing development of very dense, tall housing.
It worked REALLY well in capitalist, uber-wealthy Singapore (GDP per capita substantially higher than the USA). ~78% of Singaporeans live in housing developed by the Singapore Government's Housing and Development Board (https://en.wikipedia.org/wiki/Housing_and_Development_Board). It works a bit less well in Hong Kong, but still remarkably well considering how many people are housed in the very small area available.
But just this point is a rabbit hole of questions in itself.
If we equipped every store with tracking devices that measured the amount of time spent by people visiting (!!!!), that might incentivize making products really hard to find in the store, or making really long lines, so people spend more time there.
If it's the raw number of times people spend visiting the store, I am sure there are ways to game that too ("visit us 10 times this week for 10% off your next purchase!"). There could be laws against that, but..
First, a quick empirical quibble:
Cost-efficacy, beyond a point, is not rewarded with any increase in market share. The unfit are not selected out.
Not true, I don’t think. I have personally noticed rental rates decline in Auckland City Centre during the covid-19 period because of the abnormally low demand here, and in a Downtown LA housing boom several years ago, it was common for landlords to give away free months' rent. If the amount of supply exceeds demand by a sufficient amount, you will see market forces work. Why wouldn’t you?
I think I have two key objections, not necessarily an exhaustive list but two fairly key objections that come to mind quickly:
(1) Is there any mechanism here for actually increasing the sum total amount of high-demand property? If not, there are still going to be a large amount of people who didn't get to be located in high-demand areas. If so, is that mechanism intrinsic to the Propinquity City model or could it be implemented just as well within our current system of property ownership? For instance, I imagine this system would include rules about land use that would legally permit density where many people want to live. But there is no technical reason we couldn't implement the same rules within our current system. As one can observe in areas of cities where density is in demand and is allowed, over time, density is actually developed by the market according to demand. And that's a hell of a lot easier than developing an entirely new economic system, particularly if it also involves switching to a modular housing system.
(2) And largely as a result of my previous comment, I suspect that the increase in well-being through the implementation of this system would not be particularly large compared to more limited increases that could be obtained with more incremental land use liberalisation plans. That would limit its potential as an "effective cause area" because it would be much less tractable than other reform proposals that accomplish most of the same value as this system.
As you said, it would be very difficult to implement this in existing cities so this is limited to designing in new cities. Initially I thought this was a limitation, but then I reconsidered: in the next few decades there will be billions of people across the developing world moving into new urban areas, so there is plenty of scope for implementation if developers wanted to implement it.
It would be worth doing an analysis. I recommend, if you proceed to further develop the idea, you do an impact estimate via spreadsheet or other software. Consider the number of people likely to be impacted, the increase in well-being that would result (using QALYs or other empirical measure; be sure to consider anxiety arising from the lack of stability that people may be asked to move at any time), and the amount of political energy that would be need to be invested to achieve the calculated impact. And calculate this relative to the next best solution (maybe a classical Georgist Land Value Tax combined with liberalisation of land use would be a good baseline).
For everyone interested in using evidence to find more effective ways to give and to have a career that makes an impact addressing the world's most pressing problems.
We meet regularly every second Tuesday at 6PM. we maintain full details about events on our meetup page at https://www.meetup.com/Effective-Altruism-Auckland/
We also catch up regularly on our FB Messenger group which you are welcome to join at https://m.me/join/Abaero_uwyCzE_9m
We are building a community of people committed doing as much good as possible in life. We consider scale, neglectedness, and tractability to look for underrated opportunities to do good and then go over those opportunities. We support and care for one another to plan for the long term: building, not burnout.
I have a few technical quibbles here.
It's not quite accurate to imply Philosophical Transactions of the Royal Society B itself has made a claim about the robustness of MCB. Generally only an editorial endorsed by the editorial board should be taken as a statement about the journal's position in particular. Generally academic journals provide a forum for academic debate. Only the authors of an article are really standing behind the position. The journal only publishes work of a certain standard, and publishing a paper is somewhat an endorsement of the quality of work in the paper, but not of the finding itself.
Generally I understand it is not a given that MCB will work. Only the sulphur dioxide solution is really proven, and "sulphur" makes me nervous (I don't know if there are good grounds for that). More research is needed on MCB, which a point in favour that the research should be funded and carried out as soon as possible.
It may be that researchers could do research into MCB without it being seen as an endorsement by the entire field that we don't need other solutions. MCB can and should be presented as important experimental work that needs to be done, as a last resort. When it is actually proven, I think that's when we have the dilemma about what to tell the public. But at that point, looking at the status quo, it may be our only option left.