I heard (but can't verify) that fathers in Norway get a lengthy (many months to year?) paternity leave, as the powers that be realized that this time meant less juvenile delinquency ergo less monetary strain (and better national economy) in the long-run.

I don't know what the average parental leave duration is, but only 12 weeks are guaranteed and that is unpaid. Seems like kind of a short amount of time to make such a significant dent in your career earnings. How many promotions do you miss in 12 weeks?

On the other hand, 9% of households are single-parent and 80% of those are headed by the mother. (http://en.wikipedia.org/wiki/Single_parent) That's 18+ years of hours lost to taking care of sick kids, ferrying them to/from school and activities, not being able to work late, etc. Seems more significant to me.

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I don't know if you were actually referring to parental leave (i.e., paid time off) when you said "paternity leave" or if you were talking about a parent who actually quits his job for years at a time to raise children from birth until adolescence. This seems to be the most significant factor determining income disparity and even luxurious Scandinavian parental benefits don't completely neutralize the intense societal (and probably biological) factors that cause women to make this choice, as the article points out.