look at table 4 in the paper ( available for free here http://www.scribd.com/doc/219732275/99907-w20065 ; pg 35). The authors say, "As a proxy for two-career households, we create an indicator for households where both spouses are employed in a professional or technical occupation." That addresses the dual-income question, though I think it fails to address it adequately. The authors show that intra-state migration fell both for couples both employed and even attempts to break out prof/tech and college degree requiring employment. Nonetheless, the base year is 1981-89, and I think (even attempting to call it technical employment) that this is possibly long enough ago -- at least 25 years -- that the nature of women's employment has changed. Perhaps the nature of work of secretaries is more homogenous, less value-adding, or easier to find as compared to senior engineering leads? So as women became more the latter than the former, perhaps this doesn't control.

To the authors' point, though, this isn't a big enough fraction of the population to skew their results. That is, while the situation may well suck for dual-earner professional households, there aren't that many.