I'd be really interested to see this broken down further: * Single mothers, married mothers, single fathers, and married fathers - does being married have an i

I'd be really interested to see this broken down further: * Single mothers, married mothers, single fathers, and married fathers - does being married have an impact on productivity? If married parents produce more, then perhaps the issue is the mothers not having as much help as the fathers in aggregate. * Same sex couples vs. Heterosexual ones. Do lesbian mothers suffer from the same productivity penalty? Or do gay male faculty members take a similar hit to mothers since they're acting as primary caregivers? * Adoptive/non-biological parenthood versus giving birth: Is it being a mother that causes the dip or birthing a child?