I've worked in a few different scenarios in my life - in an academic setting, in the public sector, for a small multinational and run my own business. I was a manager for some of the time in the multinational, and I bought the argument that part time employees couldn't hold management roles. I understood that job sharing could work, but that it took a very special pair of people and that it still cost the company because it really meant 6 days a week as a result of the need for a day when both sharers are working at the same time.
Then I got to be a better manager and I started thinking a bit more clearly. I also got a better grasp of what makes good employees. If you combine the idea that people work better when they have a balanced life with the idea that roles within organisations are fluid, not fixed little boxes, you come to the conclusion that we should all move towards a norm of most people working 3 days a week.
As a manager, you look at all the work that needs to be done, and the skills required to do it. You determine how many employee days you require of each skill to get everything done. You look at the employees you've got and which skills each has. You don't have to split this job between two people, you look at subcomponents. I might share the stock management with Joe and the supplier management with Jill and Jackie. And then you keep thinking outside the square. It might be necessary in some more senior roles to be contactable on your days off. This is not that big a deal as long as everyone understands that it is for quick, urgent questions. If the role needs more attention than a 5 or 10 minute call, there needs to be someone assigned to make the decision on days when you are not there. This isn't a big deal. It's how our entire business runs, and once you get your head around it, it is absolutely no more complicated than the current paradigm.
Think of all the benfits. A wider range of experience in the workplace. Children get to see both parents during the week. They might still need one day of daycare, but for many kids this is great - a chance to be with other kids while still spending heaps of time with their parents. For those kids for whom day care really doesn't work, more flexible workplaces would also make it possible for some people to work 2 days a week, or 5 days a fortnight, or whatever schedule works for everyone. For single parents the concept of flexibility is built into the workplace, they don't have to fight for reasonable working conditions. Same goes for those people with disabilities who can work a few days but not 5. One less fight for people already fighting enough.
Of course, there are probably some jobs that really need one person doing them 5 days a week (actually, I doubt there is anything that can't be done 4 days a week, but I could be wrong), but presumably there will also be people who want to work 5 days a week. I'm not suggesting that 3 days a week should be compulsory, just that is should be the default instead of 5. Also, some people might prefer working 4 hours a day, 5 days a week, or some other combination.
And of course, there would be another massive benefit - meetings would be harder to call. Perhaps even only the necessary meetings would go ahead. And since many people might have to call into them, hearing kids in the background (or birds, or whatever) might no longer automically imply that you have suddenly lost all your professional skills.
And maybe, with not everyone always there, the ridiculous culture of working insane hours would start to abate. It isn't more productive, it just burns people out, and costs the community in terms of children raised with absent parents and reducing the diversity of people in senior positions. On that latter point, it's only anecdata, but the thread on Shapely Prose lists many examples of how women are preferentially pushed out of certain fields because of the obssessive cultures that prevail there. It obviously doesn't just preferentially push out women, it preferentially pushes out anyone looking for more balance.
All of this would require a huge shift in management technique. It would require managers to manage, rather than being a passive conduit between policy makers and the people who actually do the work, for a start. I left my last job because the Powers That Be wanted me to be the latter and I found it frustrating and infuriating, especially after the previous regime had expected me to be the former. It would be a learning curve for sure, and it would really require managers to understand the work they manage (which has to be a Good Thing), but in the end, everyone benefits. This isnt't a zero sum game. Making employee's lives better doesn't have to cost the employer.
On a final note, just because this has been all about paid work, doesn't mean that I think everyone should be in it. It doesn't mean that I think that people who are not in it are not contributing to society. Nor must they be studying to "count". Part of the motivation for this model is to share the unpaid work around more and therefore increase its value in the paid work world.