The absolute numbers seem low, but Italy being towards the bottom doesn't really surprise me. Not having a dig at them, I know lots of Italians and this is what they have told me lol (although they're keen to make a distinction between the industrious north and the lax south).

I think it's an annual average, which means it includes holidays and weekends. Maybe it also includes taxes. I don't have much time right now to check how it was calculated, but I'll take a closer look later. Thanks for bringing this up, it's a good point.

Keep in mind that this chart shows the average for all people in the working age bracket, from 15 to 64 years, whether or not they are employed.

I'm not sure how it is in other countries, but in many European countries you can't work under the age of 18 because it's compulsory to be in school. I would also add that in richer countries, people have the financial means to work less and enjoy more vacation days.