I have never met the author， Pedro Gomes， but a mutual friend asked for my address so he could send me an advance copy of a book advocating a shift to a four day work week （at the time of writing this review it has still not been published）。 I wrote back that I only wanted it if it did not commit the “lump of labor fallacy” that shortening the workweek would keep GDP unchanged but lead to more jobs and a lower unemployment rate （a fallacious idea because there is no empirical evidence for it and I have never met the author， Pedro Gomes， but a mutual friend asked for my address so he could send me an advance copy of a book advocating a shift to a four day work week （at the time of writing this review it has still not been published）。 I wrote back that I only wanted it if it did not commit the “lump of labor fallacy” that shortening the workweek would keep GDP unchanged but lead to more jobs and a lower unemployment rate （a fallacious idea because there is no empirical evidence for it and a theoretical presumption against it）。 Gomes and my mutual friend assured me it did not commit the fallacy and with that assurance in hand I was happy to get a copy。 I often just read a chapter or two of books that are sent to me but in this case I kept wanting to read more—both because of the importance of the idea， the nice manner in which it was presented， and the way in which the author’s genial and enthusiastic persona radiated through so clearly。 I uncertain by sympathetic to the argument for a four day work week before reading the book， after reading it I’m a little less uncertain， a little more sympathetic， and will definitely pay more attention to it going forward because its importance as an idea is very high relative to the amount of attention it gets （the later being virtually none）。In the 1920s there were two economic predictions that fared dismally。 The first was Irving Fischer’s October 1929 pronouncement that “stock prices have reached what looks like a permanently high plateau，” a prediction that was falsified two weeks later。 The second was John Maynard Keynes’ 1930 prediction that a century later we would all be working 15 hour weeks。 While there are a four more years to go I don’t think I’m going out very far on a limb when I predict that the typical worker will be working more than 15 hours a week nine years from now。The problem with Keynes’ prediction wasn’t the economy， it has performed towards the upper end of Keynes prediction that “the standard of life in progressive countries one hundred years hence will be between four and eight times as high as it is to-day” （as of 2019 it was seven times higher and should be nearly eight times higher by 2030）。 The prediction went wrong in that we increased our material consumption by this amount while the consumption of leisure has grown much less than Keynes expected。 For a while before and after Keynes hours worked fell sharply as people shifted from a dawn to dusk schedule to a more regulated six day workweek to （in 1938 in the United States） a five day workweek。 Since then hours have still generally trended down but in recent decades they have stabilized and for higher-wage workers have trended up。In general economists have a predisposition to trust consumer choices。 Since Keynes wrote people are spending less on three-piece tweed suits and more on blue jeans， a choice that few would judge。 But hours worked is not exactly a choice。 For a given worker it is hard to get a job and advance in the job without working full-time and in some cases even more， with full time defined as five days a week and eight hours a day。 For a business it is also not exactly a choice because it cannot just shutdown one day a week without disrupting relationships with suppliers， customers， and others。 The only way to make the choice is more collectively by shifting laws or norms so that， as the title of the book says， Friday is the new Saturday。Gomes points out that *no one* is advocating re-standardizing the workweek at something more than 40 hours a week or 5 days a week and a number of people argue that it should be decreased。 That leads him to suspect that the current number could not be an optimum （in contrast many other numbers， like tax rates， have at least a shot at being optimal given that there are arguments for both raising and for lowering them—albeit I would fall on the side of raising them）。 In his book he advocates very specifically for a new standard four-day workweek from Monday through Thursday which he views as vastly superior to a flexible four days a week because of the positive leisure spillovers and also reducing the productivity issues associated with job sharing。 He is more agnostic on what would happen to total hours and other policy design decisions。Gomes’ book is very strong on the pros for a four day workweek but mostly dismissive of the cons。 He presents the pros nicely through the eyes of different economists （Keynes， Schumpeter， Marx and Hayek—as well as a host Nobel prize winners） arguing that if they were alive today they would virtually all support a four day week， albeit for different reasons。 The presentation is pleasant to read， has a lot of easily digestible history of economic thought， and makes some points I didn’t know before。Gomes is not worried about wages and non-leisure consumption falling when hours fall， but his rebuttal is at times weak （one of his argument is that there need not be a cliff in the year it was implemented because nominal wage freezes in the years before would accomplish the adjustment， but this is simply a wage cut， another argument is that firms could reduce their profits but while that might be nice unless the conditions that generated excessive rents changed they would not actually charge them）。 I wish there was a little bit more admission that something good is worth paying for。Gomes did raise some arguments I had not thought of or had dismissed too hastily。 While the lump of labor fallacy version of job creation is wrong， Gomes semi-convinced me that in industries with declining employment （e。g。， manufacturing） the decline could be less severe if hours/days were being reduced so more workers would be retained。 Particularly interestingly， he pointed out that a lot of innovation was done by people in their spare time—and that if people had more of it we might have more creativity and innovation in different spheres。Gomes devotes a few pages to the ways that a four day school week would not worsen education or might even improve it。 This would be the area that would make me the most nervous and that I could imagine being a major unforced error。 I would not be overly judgmental of other people’s leisure choices （I’m very open minded and like people whose idea of leisure is reading economics books， classics， science fiction and even fantasy books）， but I would not trust children to make particularly good use of the extra time—let alone parents to structure good uses for them。People have been talking about a four day week for decades。 Paul Samuelson supported one in 1970 arguing that it would be a major social invention。 It is potentially a much bigger deal to a much bigger group of people than just about any economic idea currently under discussion， it deserves much more discussion， debate， and possibly even it is time to consume some of our prosperity by ratcheting down the rat race a notch。 。。。more