Author Archives: sanhei

More efficient use of rooms and equipment during the shutdown

Instead of the labs, gyms and other rooms standing empty during the shutdown, the same isolation of people could be achieved by allocating each building or other resource to one person. Equipment from gyms or labs could be lent out for the duration of the shutdown, of course keeping a database of who borrowed what and making the borrower liable for its safe return. If only one person uses each object or building the whole time, then there is no cross-contamination or infection-spreading.

Excess demand could be rationed by lottery. Only the winner of the lottery for a resource would be allowed to use the resource, with large penalties for sharing. This would improve efficiency slightly, because one person instead of zero would be using each resource.

If the heat, water and electricity were turned off during the shutdown, then it might be more efficient to let the buildings stand empty, instead of having the utilities on and one person in each building or room. However, the lights in MIT buildings are still on at night, just like before the shutdown (and it seemed wasteful back then already).

Virtual reality helmet for video calling

1 Reply

Current virtual reality headsets can display video calls, but the person wearing the VR goggles is filmed from outside these. A face with its top half covered by VR goggles is not very expressive, which somewhat defeats the purpose of a video call. The solution is a sphere around the head with the webcam inside it and the video of the other caller projected on the inside. An astronaut’s helmet is an analogy.

To prevent suffocation, the sphere should not be airtight – small CPU fans can be installed at the top or back to circulate air in and out. This also prevents humidity buildup. For headphones as well, I would prefer some ventilation of the area covered.

Multiple webcams pointed at the face allow for 3D imaging, so the video call could take full advantage of the 3D display of virtual reality headsets. However, 3D display relies on projecting a different image to each eye. If the video call is simply projected on the inside of the sphere, then it is a single image and the 3D effect is lost. One solution is to point a small data projector at each eye to display different images. Then the sphere is not needed, just cameras and projectors attached to a stick attached to a headband. A Dilbert comic had this idea, but I cannot find the link on the web.

Oxygenating blood directly

Leave a Reply

Engineering and biological constraints may make the following idea infeasible, but theoretically, one way to keep people with lung damage alive is to pump their blood through a machine that oxygenates it. Dialysis is an analogous treatment for kidney failure.

Blood would be taken out via a cannula, pumped through a system with a large surface area covered with an oxygen-permeable membrane. On the other side of the membrane is gaseous oxygen. After passing through, blood is pumped back into the body via another cannula.

The large surface area could be just two flat plates with a narrow gap between them. The oxygen-permeable plate probably needs to be thin, which makes it weak. Positioning the plates horizontally allows the pressure of the blood between the plates to support the top plate. The pressure of the oxygen above it could be regulated so the plate does not bulge outward. With careful pressure management, the plate does not have to be rigid, could be just a thin film.

The potential complications are in the details: ideally the blood would be taken from the arteries leading from the heart to the lungs and inserted into the veins going from the lungs to the heart, but puncturing these vessels is dangerous. Taking the blood from an arm or leg vein is straightforward, but there may be biological problems if oxygenated blood is pumped back into a vein instead of an artery.

Sudden lung failure does not leave enough time for such a system to be set up, because death occurs quickly without oxygen. However, if the lung failure is predicted with high probability in advance (such as when a disease is disabling the lungs), then the person can be connected to the oxygenation system and kept alive. This buys time for either the disease to be cured, in which case the lungs may become functional again, or for lung transplantation if feasible.

On the optimality of self-quarantine

Leave a Reply

Is self-quarantine early in an epidemic optimal, either individually or for society?

Individual incentives are easier to analyse, so let’s start with these. Conditional on catching a disease, other things equal, later is better. The reasons are discounting and the advances in treatment. A delay of many years may increase the severity conditional on infection (old age weakens immunity), but such long time intervals are typically not relevant in an epidemic.

Conditional on falling ill within the next year (during which discounting and advances in treatment are negligible), it is better to catch the disease when few others are infected, so hospitals have spare capacity. This suggests either significantly before or long after the peak of the epidemic. Self-quarantine, if tight enough, may postpone one’s infection past the peak.

Another individually optimal choice is to get infected early (also called vaccination with live unattenuated virus), although not if immunity increases very little or even decreases. The latter means that one infection raises the probability of another with the same disease, like for malaria, HIV and herpes, which hide out in the organism and recur. Cancer displays similar comebacks. For viral respiratory diseases, as far as I know, immunity increases after infection, but not to 100%. The optimality of self-quarantine vs trying to be infected early then depends on the degree of immunity generated, the quality of the quarantine, whether the disease will be eradicated soon after the epidemic, and other details of the situation.

Individual optimality also depends on what the rest of the population is doing. If their self-quarantine is close to perfect, then an individual’s risk of catching the disease is very low, so no reason to suffer the disutility of isolation. If others quarantine themselves moderately, so the disease will be eradicated soon, but currently is quite infectious, then self-isolation is individually optimal. If others do almost nothing, and the disease spreads easily and does not generate much immunity, then an individual will either have to self-quarantine indefinitely or will catch it. Seasonal flu and the common cold (various rhinoviruses and adenoviruses) are reasonable examples. For these, self-quarantine is individually suboptimal.

Social welfare considerations seem to weigh in favour of self-quarantine, because a sick person infects others, which speeds up the epidemic. One exception to the optimality of self-quarantine comes from economies of scale in treatment when prevalence is not so high as to overwhelm the health system. If the epidemic is fading, but the disease increases immunity and is likely to become endemic, with low prevalence, then it may be better from a social standpoint to catch the disease when treatment is widely available, medical personnel have just had plenty of experience with this illness, and not many other people remain susceptible. This is rare.

Herd immunity is another reason why self-quarantine is socially suboptimal for some diseases. The logic is the same as for vaccination. If catching chickenpox as a child is a mild problem and prevents contracting and spreading it at an older age when it is more severe, then sending children to a school with a chickenpox epidemic is a smart idea.

Reducing the duration of quarantine for vulnerable populations is another reason why being infected sooner rather than later may be socially optimal. Suppose a disease is dangerous for some groups, but mild or even undetectable for most of the population, spreads widely and makes people resistant enough that herd immunity leads to eradication. During the epidemic, the vulnerable have to be isolated, which is unpleasant for them. The faster the non-vulnerable people get their herd immunity and eradicate the infection, the shorter the quarantine required for the vulnerable.

For most epidemics, but not all, self-quarantine is probably socially optimal.

If top people have families and hobbies, then success is not about productivity

Leave a Reply

Assume:

1 Productivity is continuous and weakly increasing in talent and effort.

2 The sum of efforts allocated to all activities is bounded, and this bound is similar across people.

3 Families and hobbies take some effort, thus less is left for work. (For this assumption to hold, it may be necessary to focus on families with children in which the partner is working in a different field. Otherwise, a stay-at-home partner may take care of the cooking and cleaning, freeing up time for the working spouse to allocate to work. A partner in the same field of work may provide a collaboration synergy. In both cases, the productivity of the top person in question may increase.)

4 The talent distribution is similar for people with and without families or hobbies. This assumption would be violated if for example talented people are much better at finding a partner and starting a family.

Under these assumptions, reasonably rational people would be more productive without families or hobbies. If success is mostly determined by productivity, then people without families should be more successful on average. In other words, most top people in any endeavour would not have families or hobbies that take time away from work.

In short, if responsibilities and distractions cause lower productivity, and productivity causes success, then success is negatively correlated with such distractions. Therefore, if successful people have families with a similar or greater frequency as the general population, then success is not driven by productivity.

One counterargument is that people first become successful and then start families. In order for this to explain the similar fractions of singles among top and bottom achievers, the rate of family formation after success must be much greater than among the unsuccessful, because catching up from a late start requires a higher rate of increase.

Another explanation is irrationality of a specific form – one which reduces the productivity of high effort significantly below that of medium effort. Then single people with lots of time for work would produce less through their high effort than those with families and hobbies via their medium effort. Productivity per hour naturally falls with increasing hours, but the issue here is total output (the hours times the per-hour productivity). An extra work hour has to contribute negatively to success to explain the lack of family-success correlation. One mechanism for a negative effect of hours on output is burnout of workaholics. For this explanation, people have to be irrational enough to keep working even when their total output falls as a result.

If the above explanations seem unlikely but the assumptions reasonable in a given field of human endeavour, then reaching the top and staying there is mostly not about productivity (talent and effort) in this field. For example, in academic research.

A related empirical test of whether success in a given field is caused by productivity is to check whether people from countries or groups that score highly on corruption indices disproportionately succeed in this field. Either conditional on entering the field or unconditionally. In academia, in fields where convincing others is more important than the objective correctness of one’s results, people from more nepotist cultures should have an advantage. The same applies to journals – the general interest ones care relatively more about a good story, the field journals more about correctness. Do people from more corrupt countries publish relatively more in general interest journals, given their total publications? Of course, conditional on their observable characteristics like the current country of employment.

Another related test for meritocracy in academia or the R&D industry is whether coauthored publications and patents are divided by the number of coauthors in their influence on salaries and promotions. If there is an established ranking of institutions or job titles, then do those at higher ranks have more quality-weighted coauthor-divided articles and patents? The quality-weighting is the difficult part, because usually there is no independent measure of quality (unaffected by the dependent variable, be it promotions, salary, publication venue).

Learning and evolution switch the sign of autocorrelations

Leave a Reply

Animals are more successful if they learn or evolve to predict locations of food, mates and predators. Prediction of anything relies on correlations over time in the environment. These correlations may be positive or negative. Learning is more difficult if the sign of the correlation switches over time, which occurs in nature due to resource depletion, learning and evolution.

If a herbivore eats a tasty patch of plants or a predator a nest full of eggs, then the next day that food is not there (negative correlation), but the next year at the same time it is probably there again (positive correlation) because the plants regrow from roots or seeds, and if the prey found the nesting spot attractive one year, then other members of the prey species will likely prefer it the next year as well. However, over many generations, if the plants in that location get eaten before dispersing seeds or the young in that nest before breeding, then the prey will either learn or evolve to avoid that location, or go extinct. This makes the autocorrelation negative again on sufficiently long timescales.

Positive correlation is the easiest to learn – just keep doing the same thing and achieve the same successful outcome. Negative correlation is harder, because the absence of success at one time predicts success from the same action at another time, and vice versa. Learning a changing correlation requires a multi-parameter mental model of the superimposed different-frequency oscillations of resource abundance.

There is a tradeoff between exploiting known short-period correlations and experimenting to learn longer-period correlations. There may always be a longer pattern to discover, but finite lifetimes make learning very low-frequency events not worthwhile.

Affirmative action, unequal contests and incentives for effort

Leave a Reply

Firms using affirmative action policies may perform better because of a welcoming work environment, better candidates, peer effects in diverse teams, but also because of stronger incentives that are targeted better. Unequal standards in contests, such as a lower bar for promotion for historically underrepresented groups, may motivate greater effort than equal ones. The reasoning is as follows.

If people expect to have unequal performance, then equal standards may demotivate everyone, because the high performers think the promotion or bonus is almost assured even without further effort, and the low performers believe the prize is unattainable, so no point in trying. In this case, setting a higher bar for the better-performing group can incentivise both groups, like different divisions in sports. The result that equalising a contest motivates greater effort is fairly general in game theory. Contests may even motivate overprovision of effort relative to the socially efficient level.

A similar effort-increasing effect of unequal standards occurs even if the groups have equal performance, provided their preferences differ. For example, if men value winning a contest (for evolutionary or other reasons), then they exert greater effort in a competitive environment where some but not all can get promoted. If women care little about winning and focus on absolute compensation, then promoting all of them does not significantly reduce their work incentives. An employer who does not internalise the full cost of the employees’ effort wants them to overwork, thus in such an environment optimally sets a high bar for the promotion of men, but a low bar for women.

On the other hand, if there is a limited number of promotion slots, then it may be optimal to give all these to men, because this increases total effort in the firm the most, and use other compensation (salary, bonuses, flex-work) to motivate women.

Visually distinct social classes in agrarian societies

Leave a Reply

One argument advanced for why slavery in the US was special among the world’s slaveholding societies is that one race enslaved another. However, before the age of genetic testing, the races could only have been distinguished visually. Similarly obvious differences in the looks of slaves and masters, or serfs and nobility occurred in all agrarian societies. The obviousness of distinct looks is meant in the statistical sense: with what accuracy could people classify others into slaves and masters, or peasants and lords, averaged both across the population judging and the population judged? I believe the accuracy was close to perfect – comparable to the classification accuracy of US slaves and slaveholders – for the following reasons.

Serfs were malnourished in childhood, thus short. They did hard physical labour without stretching much, thus were bent over, with back and leg muscles better developed than the rest. They spent the day outdoors without sunscreen, wearing limited clothing, thus were tanned. The lack of sunglasses caused them to squint, creating characteristic wrinkles on the face. They seldom had opportunity to wash, thus had ingrained dirt in their skin that would not have come out with a single hard scrubbing. Both corporal punishment and intrafamily violence caused many of them to have visible scars, missing teeth, crooked noses. By contrast, the well-fed nobility were tall and practised proper erect posture in childhood for table manners and dance lessons. Their physical exercise was mostly cardiovascular, without heavy lifting, thus they were either slim or fat, but not muscular. Fencing may have developed noblemen’s quadriceps, biceps and wrist muscles, not so much the trunk. The nobility’s fashionable paleness was further ensured by wearing gloves and hats and carrying parasols during the short time spent outdoors.

All these physical contrasts ensured that even in the same clothes and surroundings, without talking or moving, a peasant and a noble could be distinguished at a glance. In this sense there was nothing special about US slavery.

The belief that US slaves were more distinguishable from their owners than those of other slaveholding societies is based on modern experience – nowadays, people of the same race but different social class are difficult to distinguish based on their physical appearance. Similar nutrition, sports opportunities and outdoor exposure lead to similar stature, musculature and tan.

Window allocation to the rooms benefiting the most

Leave a Reply

People seem to value having a window in their office or living room, more so than in a stairwell, closet or storage. It would be efficient and simple to design the floorplans to maximise the total benefit derived from windows. However, in both commercial and residential buildings, the corners (with the best window access) sometimes have stairwells or elevators instead of offices or living rooms. For example, in the MIT economics department (building E52), the seminar rooms have the biggest windows with the best view, and one corner of the building is a stairwell. In seminar and teaching rooms, people are supposed to look at the slidescreen or speaker, not out of the window, so the benefit of windows is little. Sometimes a window even adds negative value if the sun shines in people’s eyes and they have to spend a small amount of time closing the blinds.

If building regulations require a stairwell to have windows, thus be adjacent to an outside wall, then it would still be welfare-improving to locate offices at the corners, relegating the stairwell to the middle of a side of the building. Specifically, the side with the worst view or the side most prone to undesirable glare. Another way to comply with window requirements is to construct a shaft in the middle of the building (as in some New York highrises) and put the stairwells next to the shaft.

Ebay should allow conditional bids

1 Reply

Ebay should allow buyers to bid for a single item across multiple auctions: make a bid for one item, then if outbid, automatically make the same bid on the next identical (as defined by the buyer) item and so on. This increases efficiency by joining multiple auctions for identical items into one market with many sellers and buyers. It also reduces selling times, because a buyer who just wants one unit does not have to wait until being outbid before bidding for the next identical item. Buyers generally are not continuously watching the auction, so there is a delay between being outbid and manually making the next bid. Buyers are willing to pay to reduce the delay, as evidenced by purchases at “buy it now” prices greater than the highest bids in the auctions.

More generally, bids conditional on being outbid would help merge auctions into markets, gaining efficiency and speed. For example, a buyer has different values for used copies of the same item in different condition and wants just one copy of the item. Conditional bids allow the buyer to enter a sequence of different-sized bids, one for each copy, with each bid in the sequence conditional on the preceding bids losing.

Linking the bids is not computationally difficult because Ebay already sends an automatic email to a buyer who has been outbid. Instead of an email, the event of being outbid can be used to trigger entering a bid on the next copy of the item.

Faster selling times benefit everyone: sellers sell faster, buyers do not have to waste time checking whether they have been outbid and then making the next bid, Ebay can charge higher fees to appropriate part of the increased surplus from greater efficiency. Ebay can also use the data on which items buyers consider similar enough to classify products and remove duplicate ads.

A browser extension or app can provide the same functionality: an email with title containing “You have been outbid” triggers code that logs in the user (with the credentials saved into a password manager or the browser) and types in a bid on the next copy of the item.