If you look at the study (warning: PDF) you can get quantified information. Looking at page 5 you can see that a woman in .925 city (like Philadelphia) will get married a year earlier than in a 1.075 city (like Portland). So maybe the effect isn't that big after all.
Although I would expect the results would be more dramatic if we comparing the operational sex ratios of countries rather than cities. If the sexual market is unfavorable, it's a lot easier to import a mate from another city than another country.
Hrm... So the question is does data at the scale of countries (or at least larger regions within countries) exist for this?
Anyways, thanks. I may have to update a bit on this matter (conditional on poly actually being likely to cause imbalance.)
A thought occurred to me today as I skimmed an article in a rationality forum where the subject of gay marriage cropped up; seeing as the issue has been hotly contested in various public fora and especially the courts, what about poly? After all, many if not all the arguments for gay marriage apply to poly marriage as well.
Questions for LWers who are currently in a such a relationship, or have an opinion to share:
Do polies want to marry each other or do such relationships not lend themselves to permanence above a threshold of partners? Should polies campaign for the right for a civil union anyway? what are the up and down sides of this? etc