[njs12345]

I suspect this is where it comes down to anecdote and personal preference. Where we both agree I think is that (for programming especially) it's not as simple as X% more hours give you X% more work done; there are other factors at play here..

Now, I could buy a four day work week causing an overall drop in the amount of work done, but comparing them based on the same productivity is meaningless.

[yummyfajitas]

I'm not comparing based on the same productivity. I'm assuming that boilerplate (done while tired) takes 33% more time.

[njs12345]

Constant productivity with regard to working time is an assumption of the original article, it wasn't intended as a criticism of your comment.