The usual model of the effectiveness of overtime in software is described in detail at http://www.stevemcconnell.com/rdvolot.htm . Most of the direct references are not from experiment but based on observations of effective work environments.

You linked to a claim for skepticism, but did not mention the the extensive counter-examples from the first commenter, at least as it applies to some subfields of work. The quote I find most persuasive is: "The best data on sustained intellectual activity comes from financially independent authors. While completing a novel famous authors tend to write only for 4 hr during the morning, leaving the rest of the day for rest and recuperation."

That is a strong suggestion that 4 hours of creative work is about the daily limit. Why is this not a sufficient counter-argument for a broad "60 hour is optimal" recommendation? After all, a self-supporting author has good economic inventive to create more works, but this puts a limit of 28 hours per week on creative work.

Your second link is based on the Nov. 2001 newsletter of "a national firm of Construction Consultants and Claims Specialists, assisting owners and contractors in achieving profitable and trouble-free construction projects", and not, say, a peer-reviewed journal or research organization. The newsletters most recent citation is from 1992, so a bit over 20 years old, instead of a bit over 60 that you are disdainful about.

Can you find anything more recent, and research-oriented, which provides better evidence for your "60 hours is optimal" suggestion? In your analysis, please note, as the newsletter points out, that "The fatigue resulting from a daily two-hour commute is considered similar to a daily increase of two working hours.", so you can't look at a 40 hour work-week in the City of London and assume that that's the only factor to consider, if the commute takes an hour each way. (The newsletter highlights this because in some construction jobs the crew is housed on-site, so there is no commute, which makes the direct interpretation of the chart results difficult.)

Because the overcomingbias.com references didn't include more recent, and more academic/research oriented papers, I suspect both it and you did insufficient research.

In any case, I don't think you understand the math of the evidence that you report. The contracting job numbers say that it's better to hire 1.25x people, who work 40 hours per week, than it is to hire 1x people who work 60 hours per week. Assuming the cost per hour are equal - which it often is for hourly construction work - then the first gives the company more productivity for the same cost.

The only way that 60 hours per week is optimal for the company is if the workers are paid constant rates no matter how much they work per day, or if it wasn't possible to hire 25% more workers (e.g., because of the size of the site, or number of hours available to work). But that's not good incentive to get people to work longer hours, is it.

So I don't understand how you drew your conclusion that 60 hours is optimal.

Here are some of the more recent (post-1940s) papers on this topic, quoting from the CDC, which is one of the top Google hits for this topic, at http://www.cdc.gov/niosh/topics/workschedules/abstracts/daws... :

> Few studies have directly investigated the financial consequences of long working hours. For example, in a study on white-collar jobs, performance decreased by as much as 20% when 60 or more weekly hours are worked (Nevison, 1992). Data from 18 manufacturing industries in the U.S. show that a 10% increase in overtime resulted, on average, in a 2.4% decrease in productivity measured by hourly output ( Shepard and Clifton, 2000). High overtime levels can cause poor employee morale, which can affect productivity and absenteeism. For example, Circadian showed that 31% of extended hours operations that have extremely high overtime hours (25% or greater) also had poor morale, compared to only 13% of companies with low or normal overtime (Kerin, 2003). Long working hours and overtime contribute to increased worker fatigue and safety problems. For example, the average cost of workers compensation claimed per individual at extended hours facilities that reported severe fatigue problems was considerably higher ($4,037) than at facilities that report moderate ($2,240), minor ($981) or no ($276) fatigue problems (Figure 4) (Kerin, 2004).

Note that productivity is only one of the factors. Health costs, impact on family life, and accident claims are others (though the last can be included in the productivity numbers, as they seem to be for the construction numbers).

The Shepard and Clifton paper uses post-1940s data, and would be a better reference than the newsletter. I'm not paying for access to the full paper. You?

Again, don't misinterpret the 2.4% decrease from 40- to 60-hours-per-week to say that working 60 hours is better for the company than 40. If the employees are paid per hour, than it's better to hire more people than it is to have the same people work overtime. (Again, ignoring secondary effects; perhaps the factory isn't large enough for 25% more people.) Plus, the employees will have better morale, and bad morale decreases productivity.

Another, more modern review (and definitely better than a company newsletter) is "Working Long Hours:
A Review of the Evidence, Volume 1" (2003), from the Institute for Employment Studies in the UK ( http://webarchive.nationalarchives.gov.uk/+/http://www.dti.g... ). It references "Bienefeld (1972) who observed that major reductions in hours in British economic history preceded rather than followed peaks of productivity growth", though "this evidence may disputed." Still, I find nothing in there which gives strength to your "60 hours is optimal" suggestion. If anything, most of the research is aimed at determining if 35 is a more optimal number than 40.

Based on your termination of our previous exchange on the similarity of employment to a monopoly, I'm not surprised that your analysis seems weak. Your math seems wrong and your citations poor. (BTW, in that monopoly thread I've cited several economics papers which explore the model I outlined, and the developers of that model received the 2010 Nobel Prize in economics. I've also cited several papers which use the factors that you say you've never seen in economics models. This supports my belief that your analysis seems weak.)